Most diets are not nearly this effective. The potato diet seems unusually good at causing weight loss. Could it also be unusually good at maintaining weight loss after people stop eating potatoes?
There are some signs that it might. The potato diet was partially inspired by several case studies, and the case studies suggest that the weight you lose on the potato diet stays off, at least for a while. We focus on three case studies in particular:
Chris Voigt lost 21 lbs on a 60-day potato diet back in 2010. It’s not clear if he gained that back or not — this article from 2018 doesn’t mention it either way. He looks pretty lean in photos, but then again, he was pretty lean to begin with.
Andrew Taylor did an all-potato diet for a full year and lost 117 pounds. This was 7 years ago and he seems to have kept most of the weight off since then. Of course, Andrew did the potato diet for a full year, and was pretty strict about it, so his experience might not generalize to people who did the potato diet for only four weeks.
And of course, Penn Jillette, of Penn & Teller fame, lost over 100 lbs on a diet that started with a two-week period of nothing but potatoes. This was way back in 2014, and despite only doing potatoes for two weeks, he seems to have kept most of the weight off as well.
In these cases, especially the last two, it seems like the potatoes have somehow reset these people’s lipostats, the system in the brain that keeps you at a particular weight. Their lipostats used to be really high for some reason; then they did a potato diet; now their lipostat seems to be defending a set point about 100 pounds lower.
The good news is that we now have a larger sample to work with, so maybe we can finally get at some of these questions. It has been about 6 months since the close of the SMTM Potato Diet Community Trial, and this is the 6-month followup analysis.
We sent an email on January 1st, 2023 to everyone who had participated in the Potato Diet Community Trial, asking people to fill out a short 6-month followup survey.
In this survey, we asked them for:
Their potato diet participant ID, so we could connect their responses to the original results
We gave people approximately two weeks to fill out this survey. Then on January 14th, we downloaded the data.
There were a total of 53 responses by this point.
The majority (51 of them) were people who we analyzed in the original trial.
Of these, 32 were people who made it the full 4 weeks in the original trial. This happens to be exactly half of the 64 who originally made it to 4 weeks.
When we did the original analysis of the potato diet, there were still a few people who were in the middle of their four weeks of the diet, so we didn’t analyze their data at the time. Two of those people responded to this followup survey. They were not in the original analysis, but they did both complete four weeks, so we are going to include them in this analysis.
So in total we have 34 people who completed 4 weeks on the potato diet and then reported back at the 6-month check-in. This is our main group of interest.
One person (participant 24235303) reported being 136.4 lbs at the 6-month followup, but he was 222.2 lbs at the end of the potato diet, so this would mean he had lost 85.8 more pounds over the intervening 6 months. Because this seems unlikely, and because his comment was, “my weight drifted back up over a few months”, we assumed this was a typo. We followed up by email and he confirmed that he meant to type 236.4 lbs, so we corrected this number for the analysis.
Participant 63746180 reported being pregnant (congratulations!) so we are excluding her data from this analysis as her weight may not be representative.
Participant 65402765 mentioned that they “started semaglutide around the same time as potato diet”. Semaglutide (sold under brand names like Ozempic and Wegovy) is an anti-obesity medication, so while this participant did lose 13.4 lbs in this 6-month period, we also excluded their data from the analysis.
Because of these exclusions, the final sample size for the rest of the post is 32 people.
All new data and materials are available on the OSF.
On average, people gained back most of the weight they lost. This subset of people lost an average of 11.1 pounds from Day 1 to Day 28, and from Day 28 to the 6-month followup there was on average 10.3 lbs of weight re-gain.
People are on average down 0.71 lbs from their starting weight on Day 1 of the original study, but this is not significantly different from zero. On average, people are pretty much back to baseline.
In aggregate, it looks like a pretty strict reversion to the mean — people lost a little more than 10 lbs over 4 weeks on the potato diet, and gained back almost all of that weight over the next 6 months.
This is still a relatively successful weight loss intervention — you do a diet for just one month and it takes about 6 months to gain back the weight you lost. This suggests that if you were willing to do a week or two of potato diet every 3 months, you could probably keep your weight down indefinitely.
But just looking at the averages conceals a pretty drastic spread. When we plot the results, we can see that 6 months later, most people are back near baseline, maybe slightly under baseline on average. But some people are down almost 20 or 30 lbs, some people are up more than 10 lbs, and one person is up almost 30 lbs!
That central cluster is what gives us the average. Most people gained weight in the 6 months after the end of the potato diet, and ended up on average slightly under baseline.
Four people kept losing weight (one of them isn’t obvious in the plot, they were near the top of the pack at Day 28 and are near the bottom of the pack at the 6-month check-in), and three of those people ended up down more than 15 lbs over 6 months. Those three are the clear outliers below the main group at 6 months.
Five people gained back way more (10+ lbs) than they lost. These are the five dots way above the main group at 6 months, including that one dot that is up at nearly 30+ lbs.
It may be hopeless to try to figure out what is different about these eight or so people, given the small sample size, but let’s try.
Since there are so few outliers, let’s start by looking at them one-by-one.
Participants 99065049, 82575860, 66459072, 10157137, and 77742719 all ended up more than 10 lbs heavier than their baseline on Day 1 of the potato diet.
Participant 99065049 is the outlier, having lost 6.3 lbs in the trial and gained back 34.5 lbs since then, for a total gain of 28.2 lbs since Day 1. We wanted to double-check this result, so we reached out to this participant over email and he confirmed that it was not a typo.
This group didn’t say much about themselves in the comments. Only two of them left responses at all. Participant 10157137 said:
After the potato diet my cholesterol had improved, but post diet it shot back up again 😔
Participant 82575860 said:
Would appreciate a follow up post on the best potato-based recipes that were sent in
Participants 20943794, 19289471, and 35182564 lost the most weight. All of them lost more than 5 lbs on the potato diet, and kept losing weight after that. Their total weight loss by 6 months was 19.3 lbs, 23.2 lbs, and 28.7 lbs, respectively.
Participant 35182564, who lost the most weight, said:
Weight is incredibly stable, although I eat normal, just like before the potato diet. This was a great success.
Participant 20943794 offered the most detail, saying:
After the potato diet ended, I started a pretty traditional CICO diet using the Noom app. Roughly speaking, I lost 10 lbs on the potato diet, and another 10 on the CICO diet.
Before the potato diet, I tried calorie counting and various high-protein, low carbohydrate diets, and have never had this kind of sustained success. (E.g., I’ve lost 20 – 30 lbs before, but I didn’t maintain that weight for more than a month or so).
In addition to the potato diet, there are some other confounding factors:
1. Whey protein has figured heavily in all my previous diet regimens, but I obviously didn’t take any during the potato diet, and even after it ended, I drastically cut back how much protein powder I consumed (because of the lithium hypothesis)
2. Because of covid and it’s after-effects, I eat out far less frequently than I ever did before. Since January 2020, I’ve eaten restaurant food (whether dine-in or take-out) only about a dozen times (most of that was on a business trip in October 2022). Before that, I’d say I ate restaurant food on average once per week
Moving on from the comments, we can see if any of the other variables offer us insight.
The potato diet included people from all weight brackets, and maybe that’s what is causing this confusing pattern. For example, maybe all the outliers who gained weight over baseline are people who were slightly underweight when they started the potato diet, and who have gone up to a healthy weight 6 months later. Maybe all the outliers who lost extra weight were very heavy people whose lipostats were easier to reset.
But when we plot the results by BMI bracket, we see basically no pattern:
Another possibility is that this reflects whether or not people kept eating potatoes after the trial was over. After all, you can eat potatoes without being on the potato diet, and many people do. Perhaps the people who kept losing weight are the people who stuck with the potato diet, even if only casually, for the long-term. And maybe the people who gained extra weight grew disgusted with potatoes and stopped eating them entirely.
The good news is that we collected this very variable. But again, when we plot it, we see no such thing:
The person who lost the most weight ate “way less potatoes than [they] used to”. The people who gained the most weight are all in the middle. No clear pattern here.
That said, if you plot this variable WITHOUT the outliers, you see basically what we would expect — people who kept eating more potatoes are mostly still below their original weight, people who didn’t change their potato intake are back to baseline, and people who are eating way less potato than they used to are slightly above baseline.
Finally, here’s a breakdown by country. Most participants are Americans but take a look:
Most of our participants are Americans, and in the span between the start of July and the end of December there’s a major American holiday period that famously involves a lot of eating: the period from Thanksgiving to New Year’s.
As a result, at the 6-month followup our participants were asked to weigh themselves just after a period of especially serious and far-ranging eating. Quite possibly they were being asked to weigh themselves at the heaviest they would be all year.
So in some ways, the particular timing of how this all worked out is a rather conservative test of the potato diet. The weight loss from the potato diet does not seem to survive the holiday period, but it might last somewhat better across any other 6-month span.
A number of our participants commented on this as well. Let’s take a look:
(57875769) For about the first month after doing the trial my weight continued to trend downward although much more slowly. Then it slowly started creeping back up. Most of the weight came back during the holidays (it’s a little unfortunate that the six month follow up landed right after Thanksgiving, Christmas, and New Years!).
(89852176) After ending the full potato diet about 10 pounds below my typical weight, I returned rather quickly to my baseline (spurred on by eating at family vacation) and stayed there for several months. I ended the year roughly 5 pounds higher than baseline, all of which were gained in the second half of December with “typical” USA holiday (over-)eating.
(63187175) Gained about 5 pounds over the holidays, I was closer to 235 at the beginning of December
(50913144) I stayed at the lower weight for a few months, it only started creeping back up at pre-potato-trial rates in the last 6 weeks or so. I am probably going to do another round of potato intervention, i don’t like the potassium and it doesn’t seem to help me much.
(15106191) This measurement is being taken just after the holidays. This is higher than my pre-potato weight but I don’t blame the potatoes, its normal for me to weigh about this much more in January than I did in June
If we expand our plot using her data, we can see that some people were down quite a bit more in late October / early November than they were at our 6-month check in.
Some people, however, mentioned gaining the weight back more quickly:
(25547207) It took about a two months to gain all my weight back. My strength training had to cease 2 weeks in for the remainder of the study, and my large lifts dropped about 10%. It took about 1 month to recover my original strength and I was making gains before fully recovering my weight.
(72706884) I gained back all the weight within 3 months
The potato diet causes very consistent weight loss. But whatever makes the potato diet work doesn’t permanently change your set point. The first thing we see is that most people gain back the weight they lost over time, and on average, it looks like they are back close to their original weight about six months later.
Unless it did permanently change the lipostat for those three people for some reason. Because the second thing we see is striking individual differences. A small number of people ended up weighing 10+ pounds more or less than they did when they signed up for the trial, and it’s not clear why.
Maybe they had unusual life circumstances that happened to make them lose or gain more weight over those six months. Maybe they are just random outliers. Or maybe they are more/less sensitive to potatoes for some reason, more sensitive to whatever the active ingredients are. Something something cybernetic attractor states.
There’s a chance that the outliers who kept losing weight are just noise, or that they would have lost weight anyways for some other reason and just happened to sign up for the potato diet at the right time. But there’s also the chance that there is something different about these four participants. If we could figure out what that difference is, maybe we could create lasting weight loss for everyone. For example, are these four people the only four vegans in this sample? We didn’t think to ask this question, but if they were, that would be very interesting. A potential extension then would be to do a much larger potato diet study (1000+ participants) and keep special track of the people who kept losing weight after the trial ended.
Still, the potato diet is a relatively successful weight loss intervention, since one month of dieting gives consistent results that tend to stick around for about six months. And given the significant individual differences we see, it seems that for some people the effects are more lasting. While we don’t know why this happens for some people and not for others, there’s a small chance that you’ll end up being one of these outliers, and you’ll keep losing weight after the potato diet is over.
We will probably still do the 1-year followup to keep up with these outlier participants, and to see if overall average weight remains below the original baseline or not. But in general, it seems like the conclusion is that 4 weeks of potato diet will make you lose weight, and six months later most people will be back around baseline.
That’s not much weight loss, but it’s also not a very big supplemental dose of potassium, and the weight loss is significantly different from zero. People who took higher doses of potassium lost more weight, as did people who weighed more to begin with.
But what about past that first span of 29 days? Some people kept going with the protocol, taking potassium up to 60 days. Today we report their data.
30+ Days Results
We took a snapshot of all participants’ data on January 5, 2023. This was more than a month after we collected the data from the first 29 days, so everyone had the opportunity to reach 60 days by this point if they wanted to. This new snapshot is available on the OSF.
All the sample sizes in this case are too small to be statistically significant with the potential effect sizes involved, so we don’t report any statistical tests in this post.
We cleaned these raw data and are going to look at the data from Day 1 on the protocol to Day 60. Some people may have kept going past Day 60, but we aren’t going to look at that right now.
Here are the overall trajectories for the people who reported at least one day’s weight beyond day 29. The vertical red line indicates day 29, so all data points beyond that are past the span of the original trial.
Overall the trend seems to continue. One person ended up down more than 15 lbs, but that’s not at all representative.
People lost weight on average, but we already knew that. In this case we are most interested in whether they kept losing weight past the official end of the trial, so here are those same data zeroed from their weight on Day 29:
We see that in this span, people also lost weight on average, though the average weight loss was not very large. The average weight change past day 29 is negative, -0.37 lbs with all data.
See that spike up to more than 10 lbs? As you may have guessed, those are the days immediately following Thanksgiving. The participant reported that this was their “heaviest weight in 9 years”, but as you can see they lost all that excess weight very quickly.
These plots can make it hard to see what has happened for each individual, so let’s now break things down and just show their last reported weights, again relative to their weight on Day 29.
Here’s a plot of each person’s last reported day, and their reported weight change as of that day.
You can see that there are roughly two groups — most people either made it just a few days past Day 29, or made it up to very close to day 60.
We can take a special look at that second group, people who made it to Day 60 or nearly did so. Here’s everyone who made it past 50 days, broken out by just the landmark measurements — their weight on Day 1, on Day 29 at the official end of the trial, and on the last day they reported.
And here are those same data as a table:
On average, these people lost a decent bit (2.7 lbs) in the first span of the trial, and less in the second span (1.0 lbs). But this obscures a lot of individual stories that are more extreme in one way or another, like participant 42293886, who gained 3 lbs in the first leg but lost 4.6 lbs going to day 60, for a total change of 1.6 lbs. (This participant told us, “Not going to go off potassium any time soon I suspect. Making a little effort to lose weight, and it’s showing a small amount of success.”)
Also notable is that the only two people who had net weight gain by 50+ days are people who had already gained weight by day 29.
Probably the people who kept going past Day 29 were the ones who were most motivated, or who had seen the best results up to that point, so there may be some selection bias.
While none of this is super compelling, people who kept going did on average keep losing weight. They didn’t stick right where they were on Day 29 and they didn’t regress back to the mean. It’s a small amount more evidence in favor of the idea that supplemental potassium might cause weight loss, another tiny pebble on the scale.
In a practical sense, we still recommend that anyone who wants to lose weight should go on the potato or half-tato diet. It’s much more reliable, and more delicious.
Companions the creator seeks, not corpses, not herds and believers. Fellow creators the creator seeks—those who grave new values on new tablets. Companions the creator seeks, and fellow harvesters; for everything about him is ripe for the harvest.
— Friedrich Nietzsche, “Thus Spoke Zarathustra”
There’s a long tradition in the history of medicine where people figured out the cause of an industrial disease by noticing that one profession had a much higher rate of the disease than everyone else. For example, in Victorian and Edwardian England, chimney sweeps had a rate of scrotal cancer more than 200 times higher than workers who weren’t exposed to tar on the job. No, we are not making this up.
Now it’s your turn to do something similar. Your mission, should you choose to accept it, is to write a review of the mysteries on a topic and send it to us at slimemoldtimemold[at]gmail[dot]com by July 1st 2023.
Pick a topic, and write about the mysterious aspects of that topic, like we did for the mysteries of obesity in Part I of A Chemical Hunger. We mostly expect you to review topics from “hard science” areas like medicine, biology, chemistry, and neuroscience, but we are open to reviews of mysteries from social science, economics, political science, or the humanities. If you feel you can make a strong case for some mysteries and why they are mysterious, that’s good by us.
You can include Normal Mysteries, things that are unexplained but that most people know about and don’t seem all that confusing. For example, IBS and migraines are about 2-3x more common in women than in men. Everyone kind of knows this, so it’s not all that weird, but no one can really explain it, so it is still a mystery. The first three mysteries we reviewed about the obesity epidemic were all pretty normal.
You should also review Weird Mysteries, things that most people aren’t aware of and/or that seem like they totally don’t make sense, things that fly in the face of our understanding. The rest of the mysteries we reviewed about the obesity epidemic were pretty weird, like how lab animals and wild animals are also getting more obese. What’s up with that?
Our hot tip is that the simplest form of mystery is just unexplained or unexpected variation. A good example is how obesity rates vary by altitude — low-altitude counties in the United States have much higher obesity rates than high-altitude countries do. This is not predicted by most theories of obesity, and many people found this very surprising.
An unexpected LACK of variation can also be a mystery. For obesity, it feels intuitive that people who eat different kinds of diets should weigh different amounts, but diet consistently seems to make very little difference. From the perspective of the mainstream understanding of obesity, this is pretty mysterious.
How do you know that you’ve found a good mystery? It’s an emotion, a feeling that starts in your gut, not unlike IBS (which, hey now that we think about it, is pretty mysterious). Start with something that you just can’t wrap your stomach around. We’re looking for a confusion that started rumbling in your tummy when you were a student who kept asking the same basic questions and couldn’t get a straight answer, a confusion that has just kept grumbling away right there next to your esophagus ever since — now that’s a mystery. The best mysteries will be assumptions where everyone else thinks everything is fine, but you have a nagging suspicion that something is wrong.
Please focus on the mysteries of your chosen subject — DO NOT include a theory. If you feel you need to provide context, you can discuss popular theories and how your mysteries support or undermine them (like we did in Part II). But no arguing for a theory or introducing a theory of your own.
This is a mystery contest, not a theory contest. Your mystery review is the hook; if you do a great job reviewing some mysteries and win the contest, everyone will be excited to hear about your theory. Then you can put it on your own blog and get a lot of readers. If people think you have a promising direction, maybe you can get funding to study it further.
Software engineers who have just lost their jobs; grad students on strike; academics who are fed up with the paywall curtain; couples who have just retired at 35; founders whose last venture was recently acquired; billionaire playboys with too much time on their hands; anyone who is looking to make a pivot to research — this is the contest for you. You don’t need a lot of research chops to look at something and tell that it’s weird; anyone can pick out mysteries by noticing when things don’t add up, when things are unexplained, or when experts all disagree on the best explanation.
If anything, outsiders and newbies have an advantage. If your career doesn’t rely on pretending to understand, it’s easier to spot things that don’t make any sense.
We have recruited some judges to help us evaluate the mysteries: Adam Mastroianni, Lars Doucet, Applied Divinity Studies, Tony Kulesa, and possibly some other judges TBA. We will consult with these judges and will choose around 5-10 finalists, which will be published on the blog. Then readers will vote for the best. First place will get at least $2000, second place $1000, third place $500, though we might increase those numbers later on.
Use your expertise. The best entries will probably be about things YOU are already familiar with, things where you know about the mysteries the rest of us haven’t noticed yet.
All forms of media are welcome! We like to write really long stuff, and sometimes we just post our correspondence. But if you like to boil ‘em instead of mash ‘em (or stick them in a stew!), that’s cool too. Podcasts, videos, slideshows, semaphore code, etc. are all welcome. All written finalists will be published on the blog. Finalists in other formats (e.g. videos, podcasts) will be linked to. The language shared by the judges is English, so we prefer materials that suit the conventions of English speakers.
You must submit your entry under a pseudonym. This helps people discuss you and your work without having to say, “the guy or lady perhaps or person or team who wrote the SMTM mystery contest entry on pancreatic cancer”. Instead they can say, “blorpShark’s wonderful mysteries of pancreatic cancer review”, which is much nicer.
Pseudonyms also keep famous people from having an advantage. For this reason, if you already go by a well-known pseudonym on the internet, please choose a new pseudonym for this contest.
Team submissions are strongly encouraged (friendship is the most powerful force in the universe), and we encourage you to pick a band name. Go to your nearest band name generator and pick the stupidest name it generates. For solo entries, we recommend a rap name generator, like Post Malone did.
After the contest is over, if you want to connect your pseudonym to your other name(s), please feel free to do so. If you do not provide a pseudonym, one will be provided for you.
If you submit a non-written entry, please send it to us in a form that is as anonymous as possible. For example, you might send a podcast entry as an audio file, or a video essay as a video file. Don’t mention your name in the recording, etc.
Please submit written entries by putting them in a Google doc and sharing that doc with us. We will try to preserve your formatting as best we can if we publish your entry as a finalist, but no promises. If you want to make sure your formatting appears as intended, use simple formatting (e.g. bold, italics, and images). The more complicated your formatting is, the more likely we are to make an error in copying it over.
Please don’t put your name or any hints about your identity in the Google doc itself. If you do, we may remove that information or disqualify your entry.
Please make sure that the Google doc is unlocked and that we can read it and share it with the other judges. Go to the “Share” button in the upper right, and on the bottom of the popup click on where it says “restricted” and change to “anyone with the link”. If you send us a document we can’t read, we will probably disqualify you.
Frankly we reserve the right to disqualify entries for any reason, or no reason at all.
If you win, we will send you your prize money in the form of an envelope stuffed with cash, or something else if we agree that it’s more convenient.
Your due date is July 1st, 2023. If you have any questions, ask in the comments so other people who have the same questions can see. You can also email us or ask us questions on twitter. Good luck!
In November 2021, we finished our series A Chemical Hunger, where we argue that the obesity epidemic is the result of environmental contaminants, and that one of those contaminants might be lithium. We hadn’t really expected anyone to read it. But we were wrong — tens of thousands of people have now read the series, and to date the twitter thread giving an overview of the series has more than 2 million views.
Potatoes are really high in potassium, so we wondered if potassium could be the active ingredient causing the weight loss in the potato diet. We decided to try a self-experiment where we took small amounts of potassium salt every day, but it seemed unlikely that such tiny doses could have any effect. But we were wrong — we each lost about 5 pounds over four weeks. One of us kept going and lost 12 lbs over 60 days.
The goal of this study is to see if the large doses of potassium found in potatoes could plausibly be the reason why people lose weight on the potato diet.
The doses of potassium in this study are small in comparison to the potato diet, only a few thousand milligrams per day. This is much less potassium than people got on the potato diet, so we don’t expect the effect to be large in any practical sense. In fact, we expect that if there is an effect at these doses, it will be quite small, probably a loss of only a few pounds on average. We are just looking to try to see if there is any effect at all.
We are studying potassium because it is a major variable from the potato diet that we can easily look at in isolation, not because we think potassium will be a great or a practical treatment for obesity on its own.
We don’t expect everyone to lose weight on this protocol, or for it to be sustainable in the long term. We just want to know if potassium could be the reason why people lose weight on the potato diet, something that we currently have almost no information about. If it looks plausible, that tells us something about why the potato diet works; and then we can consider, ok wait a minute, why would potassium cause weight loss at all? But more speculation on these points after we look at the results.
Raw data, the analysis script, and study materials are available on the OSF. The dataset is very rich and there’s a good chance that we haven’t found everything there is to find. So if you are statistically inclined, after you’ve finished reading this post we encourage you to download the data and have a look for yourself. If you find anything interesting, or even if you’re just able to confirm our findings, you should write up your analysis on your own blog and let us know about it! Science is a game, please play!
If you recreate these analyses at home, your results may be slightly different than ours because three participants asked that their data not be shared publicly.
Whether or not you like what we’ve done here, we encourage you not to take our word for it. Download the data and materials, perform your own analysis, share your criticisms, run your own study. If you think you can do a better job, maybe you are right! Show us how it’s done.
We collected variables at three points.
First, we collected demographic variables at signup. The variables we collected at this point were:
reported hormone profile (so we can distinguish trans participants with less ambiguity)
age in years
race/ethnicity (from a limited number of options)
local postal code
current country of residence
whether they had done any sort of potato diet in the last year
In response to this last question, the majority told us they had not done any potato diet in the last year, but 40 told us they had done some kind of potato diet on their own, and 7 said they took part in our Potato Diet Community Trial.
After signup, we had people track a number of variables about their health and their diet (and how much potassium they were taking) over the course of the study, on a spreadsheet we provided. You can view a version of that spreadsheet here.
The main variables collected on this sheet were:
weight (in the morning)
potassium doses (up to four doses a day)
variables for whether or not participants consumed meat, eggs, dairy, leafy greens, and tomato products each day (just a 1 for “ate it today” and a 0 for “didn’t eat it today”), because we suspect these foods may be high in lithium (though we’re not sure)
We also included fields for several bonus variables, which were optional but encouraged. These variables were:
waist circumference (which a couple people asked for after the potato diet)
energy, mood, and ease of study (all on 7-point scales)
systolic and diastolic blood pressure
total Cholesterol, as well as LDL and HDL cholesterol
resting heart rate
fasting blood glucose
estimated hours of sleep the night prior
sleep quality the night prior
fidgeting (on a 1-7 scale)
estimated minutes of exercise
(and several fields for notes)
After we took a look at the data, we realized we had a few questions about aspects of the study that we hadn’t really measured. For example, some people mentioned that they hated the potassium while other people mentioned finding it delicious. But most people didn’t mention this aspect at all, so it would be hard to conduct any analysis related to how much people enjoyed the potassium.
So finally, on December 3rd, we sent a followup survey asking about some of these remaining questions. Five days later, there were 105 responses. We downloaded these responses and added them to the dataset.
The variables we collected at this point were:
what potassium compound they had primarily consumed
what form they had taken it in (e.g. salt vs. capsule vs. tablet)
what brand of potassium they had primarily consumed
what delivery methods they had used (e.g. in food vs. in a drink)
change in their appetite
how much they enjoyed the potassium at the beginning of the trial
how much they enjoyed the potassium at the end of the trial
whether they felt leaner or chubbier subjectively
whether they were intentionally exercising or eating more or less during the trial
whether they were on some other diet or routine when they started the potassium trial
and a free-response question asking if there was anything else we should know
For more detail, see the copies of the materials available on the OSF.
As a reminder, the main study protocol was:
Start with two doses of 330 mg potassium (1/8 tsp Nu-Salt) on the first day.
If you feel fine, try three or four doses of 330 mg potassium (1/8 tsp Nu-Salt) on subsequent days.
If you’re feeling fine after 4-7 days, try one dose of 660 mg potassium (1/4 tsp Nu-Salt).
If you still feel good, keep increasing your dose by small increments. For example, if you are on two doses of 660 mg (1/4 tsp Nu-Salt) a day, you might increase that to three doses of 660 mg, or one dose of 660 mg and one dose of 1300 mg (1/2 tsp Nu-Salt). If a higher dose makes you feel bad, try returning to the dose you were on before and maintain that.
Try slowly increasing to two doses of 1300 mg (1/2 tsp Nu-Salt) a day. Only go beyond that if you are feeling totally fine.
You should calibrate based on your own experience — different people will have different needs and different limits. For example, we’d expect someone who weighs 300 pounds would be able to tolerate higher doses than someone who weighs 150 pounds.
If you feel weird / bad / tired / brainfog and you can’t tell why, try:
drinking some water;
getting some sodium;
and see if any of those help. It may be easy to end up needing food / water / salt and not notice.
If you still feel weird, try dropping to a lower dose or taking 1-2 days off.
If at any point you feel sick or have symptoms of hyperkalemia, stop immediately and seek medical attention.
Participants were asked to record their weight every morning, and they were asked to record data up to the weight measurement on the morning of day 29 regardless of whether they stuck to the protocol. That way even if someone found the potassium intolerable, we could still use their data.
A total of 305 people submitted the initial form.
Of those, 15 people filled out the signup form incorrectly in such a way that we couldn’t sign them up (they didn’t enter an email, didn’t enter critical data such as height, etc.). We enrolled the remaining 290 people in the study.
Of the 290 people who were enrolled, 57 never entered any data on their spreadsheet, leaving 233 people who entered at least one day of weight data.
The most common outcome in this group was to make it the full 29 days, but the majority of the 233 people who entered data on day 1 stopped entering weight data before day 29. Here’s the distribution of days completed (as measured by last weight entry) from that group:
As shown above, 104 people entered weights on both the first day and on day 29. This was the criteria we specified in advance for the group we would focus on for the main analysis. Specifically, we said:
Anyone who records data for 29 days is clearly taking the study seriously, even if they weren’t able to stick to the potassium supplements the whole time. … Based on this, our main analysis will focus on participants who provide 4 weeks of data. If you provide a weight measurement for the morning of day 1 and the morning of day 29, so we can calculate your weight before and after, and you took at least one dose of potassium, we will do our best to include you in the analysis.
5. Weight Loss
The main outcome of interest is weight change by the morning of day 29. Here’s the histogram of that variable, with a black vertical line at 0 lbs (i.e. no weight change over 29 days) and a red dashed vertical line at the mean weight change:
On average, people lost weight. The mean is -0.89 lbs, or an average loss of 0.89 pounds over 29 days. With a sample size of 104, this is significantly different from zero in a one-sample t-test, p = .014, and the 95% confidence interval for average weight change is [-1.59, -0.19] pounds.
However, this obscures the data of several people who made it to the end of the study, but who mistakenly didn’t report a measurement on day 29. If we look at the data of everyone who reported a weight on day 28, this is the histogram:
This has a mean of -0.85 lbs and a larger sample size, and is also significant, p = .016.
The same thing is true if we look at everyone’s weight at day 27 — the average weight loss is 0.86 lbs and this is significant, p = .016. The exact cutoff doesn’t matter, which indicates that the result is robust.
People who dropped out before reaching the end of the four weeks also seem to have lost weight on average. You can see that the majority of people who stopped before day 21 are below zero (the horizontal line), indicating they lost some weight over the time they spent on the trial:
In fact, if you look at the weight change from EVERYONE who reported at least two weight measurements (i.e. not including those people who only reported weight for day 1, who literally could not have seen weight change), people still lost 0.79 lbs on average. Here’s the histogram:
Because of the much larger sample size, this is still significant. In fact the p-value is quite a bit lower (p = .0002) and the 95% CI is noticeably narrower, [-1.20, -0.38] pounds.
The average weight loss here is smaller, but remember that about half of these people did not make it the full four weeks! In fact, this analysis includes 26 people who didn’t even make it 7 days.
Looking over the course of the study as a whole, it appears that people slowly lose weight over time, with no apparent changes in the trend:
Of interest here is that the 95% CI excludes zero for the first time on day 7, and that day 25 is the point of greatest average weight change.
Looking at individual trajectories is a right mess, but here’s the plot anyways:
On average it looks like people lose about 0.8 lbs over four weeks on this protocol. This isn’t much weight loss, but it’s statistically distinguishable from nothing.
But obviously some people do lose more weight, sometimes a lot more. Three people lost more than 10 lbs. It’s clear that there is a lot of variation around the small average weight loss. Can we figure out what caused any of this variation?
Well for one thing, some people did not have much weight to lose to begin with. Here’s weight change on day 29 compared to starting BMI:
As you can see, people who started with higher BMIs lost more weight. This correlation is significant, r = -0.269, p = .006, and is exactly what we would expect. People who have a BMI of 22 don’t have much weight to lose, so we should expect to see very little weight loss from them, perhaps no weight loss at all. Meanwhile people with higher starting BMIs have more to lose. It’s interesting to see that the person with the highest starting BMI also lost the most weight.
Many lean people participated in this study, and most seem to have signed up because they wanted to contribute to the research even if they were unlikely to lose weight. This isn’t an experiment, but some of them do provide a sort of baseline response. “I am happy with both weights,” said one participant, “and wasn’t expecting or hoping for a big weight loss number. I thought of myself as somewhat of a ‘control group.’”
If this were a “normal” study, and we were “normal” researchers, we probably would have restricted signups so that only people with a starting BMI of 30 or higher (technically obese) could sign up for the study.
If we had done that, here’s what the analysis would look like. Unsurprisingly, this group lost more weight on average:
The average weight loss for participants who started the trial with a BMI of 30 or above was 1.83 lbs, and again this is significant, p = .031.
Another thing that might matter is what country people are from. This is especially interesting from the perspective of the contamination hypothesis, because we suspect some countries have more contaminants than others. We tried doing a “USA vs. all other countries” analysis, but that was not significant, p = .341. There also doesn’t seem to be a clear effect of what continent people are on, but we can still plot these data:
Nothing groundbreaking here, but we do want to note that we see much less variation in Europe than in North America.
But of course, the main thing we should expect to make a difference in the results of the potassium trial is the amount of potassium!
In this study, everyone was on the same protocol, but some people took much more potassium than others. People were asked to start with two doses of 330 mg on the first day and slowly work up to two doses of 1300 mg a day, but they were asked to drop to a lower dose if a higher dose made them feel bad, and to only go beyond two doses of 1300 mg per day if they were feeling totally fine. We also asked people never to go above 1300 mg in a single dose or 5200 mg in a day.
Given this protocol, it’s natural that some people ended up on higher doses than others. Here’s the distribution of average daily doses for people who made it the full four weeks:
As you can see, there is considerable variation.
With this information, we can compare the amount of potassium people were taking to the amount of weight they lost. When we do, we see a clear relationship, where people who took more potassium lost more weight on average:
This relationship is statistically significant, r = -0.276, p = .005. This is not an experimental result, since we didn’t assign people to different doses, so we shouldn’t assume it’s causal. There are certainly alternative explanations. For example, there may be weird selection issues. People who chose to take more potassium could have been the people who were like “I feel fine, I’ll take more” or people who were like “It’s not working, I’ll take more” or people who were like “I’m losing a little bit of weight, so I’ll take more and lose more”. But this result is also consistent with what we would expect if potassium supplementation was causing the weight loss.
Let’s stop a minute and take a closer look. The regression line here is y = -0.0011x + 1.3110. Essentially what this means is that the model says that on average you would gain 1.3110 lbs if you supplemented no potassium at all for 29 days, but you lose 0.0011 lbs for every mg per day you supplement above that baseline.
For example, someone consuming 2000 mg per day would lose 2.2 lbs more than baseline; since baseline is 1.3 lbs gained, we would expect them to lose about 0.9 lbs on average over 29 days.
The potato diet gives exceptionally high doses of potassium. Sources differ on exact numbers, but the USDA says that a medium potato has about 900 mg of potassium and about 160 calories, so 2000 calories of potatoes a day would give a daily dose of about 11,000 mg potassium.
Plugging that dose into the linear equation above, the predicted weight loss on the potato diet (i.e. on a dose of 11,000 mg/day) would be:
Realistically, the fact that the linear equation in this case lines up with the potato diet so well is just an amusing coincidence. The 95% confidence interval on the slope is [-0.0019 to -0.0003], so model fits for 11,000 mg/day include anything from 19.6 lbs to 2.0 lbs lost.
But you have to agree, it is amusing.
This is in fact moderate support for the idea that potassium is the only active ingredient in the potato diet. We say moderate because it’s certainly not conclusive, but it would be hard for the data to be any more consistent with that interpretation.
Another interesting comparison can be found in the relationship between weight loss and total potassium taken over the course of 29 days:
This relationship is also significant (r = -0.209, p = .033), though it’s somewhat smaller than the relationship between weight loss and daily average potassium. This may mean that taking a consistent dose is more important than the amount of potassium you take overall, though the confidence intervals of the two correlations clearly overlap, so don’t conclude too much from this difference.
Other than starting BMI and potassium dosage, we can’t really tell why some people lost more weight than others. Sex, reported hormone profile, age, ethnicity, previous experience with the potato diet — none of them seem to matter.
We asked people to report how often they ate meat, eggs, dairy, leafy greens, and tomato products, and while there are sometimes vague trends, none of these variables are ever significantly associated with weight loss. On the other hand, we should note that these were measured in a very rough fashion (just “did you eat it or didn’t you” for each day), so the variables aren’t sensitive enough to detect anything less than a very strong effect.
We also tried looking at all these variables while controlling for starting BMI and daily average dose, but there still don’t seem to be any associations with these variables and weight loss (though it’s possible we’re missing something.)
Similarly, we looked at the variables from the followup survey, but with the exception of one appetite result we will report below, we didn’t find any associations with these variables and weight loss. Even if there were relationships, we probably wouldn’t find them in these data, because there wasn’t much variation in these variables — most participants took potassium in about the same ways and (per our request) didn’t change their diet or exercise during the trial.
Ease of Weight Loss
So much for absolute weight loss. But what about relative weight loss? Were there signs that the potassium made it easier to lose weight?
Indeed there were, at least in the self-report data. Some people mentioned being surprised at how easy it was to lose weight, and some people mentioned that they were surprised they didn’t gain weight given how poorly they were eating:
(77174810) First of all – holy shit! It’s amazing how well this worked and it’s also surprising that it’s never really been studied before! Thank you for the analysis and thought that you put into this. For this trial, I basically just ate whatever I felt like, went to a football tailgate party nearly every weekend with lots of beer and foods you would not associate with dieting… and still lost nearly 10 lbs! I plan to continue on for at least another couple months so feel free to follow up later if you want to.
I have tried every diet/exercise and variation of CICO, atkins, keto, IF, etc., etc., etc. to try and lose weight. To no one’s surprise, nothing really worked for long and the weight always came back. At the end of 2020 I was over 275. It took me three months of busting my ass to lose 20 pounds and as soon as I started eating “normally” again, I slowly started putting weight back on.
(23881640) I started a quick calorie-restricted diet before the holidays (got to fit into those festive pants!), and I’m combining counting macros, counting calories, AND adding 1 tsp of potassium chloride a day to my water, and the weight is coming off. It’s making the calorie restriction much more bearable. I can tell I’m technically hungry, but adherence is so much easier doing it this way. (I lost 20 pounds before by counting macros, and that was hard.)
(60114890) Trial was very easy. Lost 5.5 lbs.
I definitely attempted to run a calorie deficit. So, this was a deliberate weight loss attempt. I’ve lost the same 5-15 lbs. maybe six times over the last 30 years. This was the first time it wasn’t really painful and didn’t require a lot of discipline. It’s also the fastest rate of weight loss I’ve experienced (1.5-2 lbs/week as opposed to 0.75-1.0 lbs/week). Very very easy. Why? Mostly appetite suppression. Historically I have been able to run 500 kcal deficits with a lot of effort. I was able to run 750-1000 kcal deficits with almost no effort. Real appetite suppression kicked in after second week, at levels of about 1800mg additional potassium. It was ridiculous—yesterday I ate 1300 kcal and burned 2600 kcal and wasn’t really hungry.
…for my purposes, I don’t really care if its placebo. My appetite was substantially suppressed. It was easy to run a 750kcal deficit. I’m going to stay on the diet until I’m at target weight of 185lbs, which would be total loss of 13.6 lbs. Feels very doable.
This wasn’t a universal experience, but we think these reports were interesting.
It seems possible that for most people, small doses of potassium aren’t enough to cause weight loss by themselves, even if they affect your appetite (see below). But they might still be helpful because they enhance other weight-loss approaches.
At this point we would like to draw your attention to the beverages known as “ketoade” and “snake juice”.
It’s possible that the keto diet works but is hard to stick to, and that ketoade has become popular because it makes weight loss on a restrictive diet much faster and easier. It’s also possible that the keto diet doesn’t cause weight loss at all, and that most successes on the keto diet actually come from people who are taking large amounts of potassium “on the side” as ketoade.
Snake juice is a term for (you guessed it) home-made electrolyte drinks people sometimes take as part of various weight loss strategies, including intermittent fasting, keto, and something called the… snake diet. As far as we can tell, no snakes were harmed in the making of this diet — it appears to refer to how snakes go a long time between meals, since it’s a weight loss strategy about going a long time between meals.
Anyways, snake juice involves drinking a concoction that gives you several thousand milligrams of potassium every day. See this helpful instructional video to learn more. It opens with a man yelling “hey FATTY, behold!” at you, so you just know it is a trustworthy and authoritative source.
In any case, most participants in the potassium trial were essentially drinking ketoade / snake juice / whatever you want to call it: potassium salt and sodium salt mixed in some beverage, often with a little bit of flavoring. And while the effect size was small, on average it seemed to cause weight loss, even without keto or fasting or anything else.
The results of this study suggest that the ketogenic diet community, and this community of “snake people”, have correctly developed a folk wisdom tradition of taking large doses of potassium to amplify their weight loss routines. If so, that is pretty wild, and it speaks well of the value of folk wisdom in solving people’s real problems.
It’s especially interesting that their theories of obesity don’t seem to point at potassium at all. These people don’t think that potassium is the active ingredient here, and they don’t have any idea why potassium might help them lose weight, but they have figured out that they should take it. That’s pretty impressive.
The inverse is true as well. The fact that internet people have settled on potassium salt as part of their folk weight loss routines supports our finding that straight potassium causes weight loss.
6. Effects Other Than Weight Loss
People mentioned a wide variety of effects, but most effects were only mentioned once or twice. One person said that the potassium made their tinnitus worse, but there doesn’t seem to be any sign of this generalizing to other participants.
We did let people report some bonus variables, but most of these variables didn’t get many responses, so we often didn’t end up with a big enough sample size to analyze. For example, only one person reported their total cholesterol on day 29, and no one reported HDL cholesterol, LDL cholesterol, or triglycerides on day 29. So we won’t be taking a closer look at any of those.
Even so, a few things did come through. Here are the effects that people mentioned more than a couple times in the self-report data, or where there were enough measurements to make taking a look worthwhile:
The most commonly mentioned effect of potassium was reduced appetite.
(36100230) I found that my appetite was dulled a bit — My mind focused on food a bit less, I snacked less between meals, and ate slightly smaller servings. I found this started to wane a little bit towards the end of the month — not entirely, but I found myself more likely to feel hungry between meals.
(58007117) Taking the potassium was very easy (with the exception of the few times I put nu-salt into pill casings and took it that way – this caused stomach pain, which I did not experience when just taking it dissolved in liquid). My overall impression is that potassium acts as a mild appetite suppressant.
(11538897) I didn’t think of food while doing the trial. At the lower doses, my hunger was affected but my appetite was not. At the higher doses, both were affected. … There was a huge difference in my general desire for food if I took the supplement in the morning before eating. If I took my first dose with food, I would be thinking about food sooner (though I wouldn’t say it was even hunger, just craving). When I took only the supplement and then went to work, it was almost always that I wouldn’t think of food until after work.
(77174810) I settled on 3 doses of ~990mg (3/8 teaspoon) a day at 0730, 1130, 1600. I felt like this kept hunger at the lowest level overall and was easy to stick with. I found that if I took the supplement when I was already hungry, I’d eat more overall. So I take the dose an hour or so before I’d normally eat a meal.
(19620767) Finished the trial. It was weird, I lost a pound the first day, then nothing for a week, then 4 more pounds, then nothing. My appetite was pretty suppressed the whole time, but due to injury and illness I wasn’t really able to exercise beyond going on walks and doing my PT, I also ate an unusually large amount of junk food for life reasons (depression, birthday cake, etc) without gaining any weight.
(18556224) The potassium didn’t magically decrease the calories I took in — I had to consciously restrict them, or have circumstances dictate that — but it did suppress my hunger, i.e. four weeks I was as hungry during the day (mostly not at all) no matter how much food I had eaten.
I haven’t decided whether the weird feeling that potassium gives me is better or worse than the hunger I’d otherwise experience, since I’ve gotten fairly good at handling that.
I haven’t noticed any cravings during the trial, which is good because that is often a problem for me — not craving things carby things, but craving certain foods I eat anyway (butter, cheese) so that I eat more calories than needed, even though I’m not really hungry for anything, just seeking pleasure.
(49045265) I did notice an reduced appetite. There was only one day during the study I was hungry.
(60114890) I definitely attempted to run a calorie deficit. So, this was a deliberate weight loss attempt. I’ve lost the same 5-15 lbs. maybe six times over the last 30 years. This was the first time it wasn’t really painful and didn’t require a lot of discipline. It’s also the fastest rate of weight loss I’ve experienced (1.5-2 lbs/week as opposed to 0.75-1.0 lbs/week). Very very easy. Why? Mostly appetite suppression. Historically I have been able to run 500 kcal deficits with a lot of effort. I was able to run 750-1000 kcal deficits with almost no effort. Real appetite suppression kicked in after second week, at levels of about 1800mg additional potassium. It was ridiculous—yesterday I ate 1300 kcal and burned 2600 kcal and wasn’t really hungry. …for my purposes, I don’t really care if its placebo. My appetite was substantially suppressed. It was easy to run a 750kcal deficit.
(06769604) My appetite was clearly suppressed, especially in the morning. The issue seemed to be that it would come roaring back in the afternoon and I’d be quite hungry.
This was true even for many people who didn’t lose weight, or who lost only negligible amounts. But it wasn’t universal, and some people explicitly mentioned that there was no change in their appetite.
We found this interesting, so we included a question about appetite changes in the followup survey. In these data, the majority of people reported no change to their appetite, but about a third reported decreased appetite, and six people reported greatly decreased appetite. Only one person reported any amount of increased appetite.
And you probably won’t be surprised to see that reduction in appetite was associated with weight loss:
When we treated this self-report measure as a continuous variable on a 1-5 scale, the relationship was significant, r = 0.295, p = .011. But you’ll also notice that many people who did not lose any weight still reported a reduced appetite, suggesting the potassium had some effect for them, just not enough to cause weight loss.
You might think that potassium caused weight loss because it reduced appetite, which caused people to eat less, which caused weight loss. That may be the case, and several people did mention that they were running a calorie deficit. But we also included a field for people to track their calories if they wanted to, and while only 22 people provided complete data, the correlation in that data is nonsignificant and pretty flat, r = -0.100, p = .659.
You’ll also notice that it’s trending in the “wrong direction”, where people who reported eating more also lost more weight.
We don’t think it’s helpful to conclude that potassium is “just an appetite suppressant”. Clearly it is an appetite suppressant, but like, um, why? Why would it do this? Everything has a mechanism. What is the mechanism for this?
We think potassium reduces appetite because it turns down your lipostat. As we said with the potato diet,
[Reduced appetite] is NOT an explanation any more than “the bullet” is a good explanation for “who killed the mayor?” Something about the potato diet lowered people’s lipostat set point, which reduced their appetite, which yes made them eat fewer calories, which was part of what led them to lose weight. Yes, “fewer kcal/day” is somewhere in the causal chain. No, it is not an explanation.
But even if we accept that potassium turns down your lipostat, you still have to ask, why does it do THAT? What is the mechanism that makes potassium turn down your lipostat’s set point? Well, more discussion in a minute.
Some people mentioned noticeable improvements to their sleep.
(24646801) Regarding sleep, in the month or two prior to the study, I had started to wake semi-regularly (5-6 nights/week & 1-2 times per night) to use the toilet. This tapered off rather quickly during the trial and with few exceptions has not returned. I don’t know enough medically to explain why this would be, but it’s definitely an improvement to my sleep, and I would continue the trial indefinitely to retain this result.
(81847724) Sleep is highly subjective but overall I think my sleep quality improved during the experiment, generally sleeping longer without waking up in the middle of the night.
(87352273) Sleep was the most pleasant surprise. I have issues with insomnia, so I tend to stay awake until 2-3 am when I get really sleepy so I don’t end up just lying awake in bed getting frustrated. With ~2000 mg of potassium as well as magnesium before bed, I found myself naturally getting sleepy and falling asleep around midnight every night without much effort or thinking about it.
We included some bonus variables about sleep in the spreadsheet, but the results are inconclusive.
Sleep quality did go up by 0.2 points, but that was not significant (p = .480).
Hours slept went down somewhat, which is interesting, but that change also was not significant (p = .296).
We should note that most people did not report either sleep variable, so the sample size in both of these cases is less than 40. It looks like potassium may improve your sleep a little and/or may help you sleep less, but this isn’t well-supported and even if there is an effect, the effect is probably small.
This is interesting given that Gwern, who is notorious for his attention to detail, did a self-experiment with potassium citrate and “confirmed large negative effects on my sleep”, with a large apparent effect (d = 1.1). Possible differences may come from the fact that Gwern was originally taking potassium in the evening rather than in the morning, and when he tested this he found a difference; was taking about 4000 mg a day, much higher than most people in this trial; and that he was taking potassium citrate, while most people on this trial were taking potassium chloride. (Also Gwern may just be built different.)
We didn’t find any effect of fidgeting (if anything, people fidgeted less over time), but there were a few self-reports of intense or manic energy.
(87352273) I had really noticeably elevated energy at first, and pretty regularly had the urge to walk or exercise just to burn off some of the nervous energy. The intensity leveled off after the first week or so, but energy overall stayed higher than usual.
(84130320) I had a huge rush of energy, like borderline hypomanic, and I ended up pulling a chest muscle doing pushups because I felt like I was 10 years younger (note to others: you are not actually 10 years younger, do not suddenly do a bunch of pushups). So that sucked.
(93059017) I had so much energy after work that I just needed to walk and I walked an extra mile home.
The participant who lost the most weight (81847724) was also notable for this report:
My mood and energy have been nothing short of fantastic. On a normal day pre-trial, I’d rate my average mood and energy levels in the 4/5 area on the 1-7 scale. Somewhere during week 2 of the trial, I really noticed how elevated I felt in my mood all day long and generally my energy levels were high regardless of the amount of sleep.
However, this increased energy did not seem to be widespread, and some people specifically mentioned not feeling any more energetic.
Looking at the self-report question we included about energy (though FWIW, a sample size of only 29), people’s energy improved by 0.54 points on a 7-point scale, but this was not significant (p = .126).
A couple people noted stimulant-like effects, and strangely, some also mentioned a kind of stimulant reduction or substitution effect.
(36100230) I felt a little more focused after taking the potassium. A few times I wanted to get some caffeine, and took potassium instead, and no longer needed the caffeine.
(72706884) My caffeine intake decreased substantially during the early part of the diet. I typically intake 100-250mg of caffeine daily. This was reduced to 30-60mg every other day during the first 2 weeks. I found supplementing with a 200mg caffeine pill helpful and used one daily during weeks 3 and 4.
(64983306) While taking potassium, I also experienced heightened concentration abilities, as if I was taking ritalin/adderall. This feeling would last for 2-3 hours after taking a dose of potassium.
We can corroborate this with our own experience. Caffeine seemed to have less of an effect for us while on the potassium, and weirdly, seems to have less of an effect still! Not sure what’s up with that.
Only seven people reported their blood pressure readings on day 29, so there wasn’t enough data to do a proper analysis.
However, most of them saw their blood pressure go down, so we figured we should go into some detail anyways.
In the seven cases that reported their BP on both day 1 and day 29, people saw their blood pressure go from:
120/81 to 113/77
114/64 to 116/63
121/91 to 114/78.5
123/90 to 123/80
131/78 to 130/85
111/75 to 99/82
121/78 to 126/81
On average, systolic BP went down by 2.9 points, with a maximum of 12 points down; and diastolic BP went down by 1.5 points, with a maximum of 12.5 points down.
Again, these differences are not significant. But with the very small number of people reporting BP, the sample size isn’t large enough to reach statistical significance. Most of these people also had relatively low blood pressure to begin with, so it’s not clear what kind of change you might see if you had hypertension.
People were split on the potassium. Many people found it distasteful, and some people hated it.
(50612600) this is way too disgusting to drink
unbelievable it’s sold as a food product
(79606462) it truly does taste horrible, even dissolved in 12 oz water
Unsurprisingly, many of these people chose to end the trial early, and we can’t blame them.
On the other hand…
(02689028) does liking kcl salt too much count as anything important
(84130320) My experience overall was actually very pleasant. I didn’t think the taste of the KCl was nearly as bad as advertised. To me, it tasted like salt, if salt were perishable and had spent a little bit too long in the refrigerator. Putting it in sparkling water was fairly good, I could tell it was weirdly salty (especially once I got up to 1300mg/dose) but if I just chugged a little, like half a glass, and then topped it back up it was legitimately delicious. If I did a schorle (fruit juice mixed with sparkling water) instead I could barely taste it. … when I felt really bad and backed off of the potassium per the instructions, I craved potassium. Like I really wanted to eat bananas and was like “boy I could really go for some sparkling water with KCl in it.” It was super strange.
(23578149) I went from finding Nu-Sal revolting (even mixed 2:1 with salt) to finding it pleasant.
But one thing is for sure: it really makes you pee.
(7619655) Have you ever eaten a really salty meal, like pizza or Chinese food, and then felt really thirsty afterwards? That’s how the potassium made me feel a lot of the time. It was drink, pee, drink, pee, drink, pee all day. If I didn’t keep up on the drinking, I would get parched lips and a headache. It was hard to keep this up, so I skipped a bunch of days towards the end.
(74537321) I found I had to pee a lot more often depending on how much water I was drinking. I tried to drink a lot of water throughout the day so I could get the most out of my bowel movements, but one issue was I just had to go pee a lot more. It felt like I would drink a cup of water, and then 20 mins later have to pee like I hadn’t gone all day. 🙂 I would say I had 1 to 2 liters of water per day in addition to meal time drinks (milk, juice, diet soda).
We found these self-reports interesting (also hilarious) so in the followup survey, we explicitly asked people how much they enjoyed the potassium. Because some people mentioned that their opinion of the potassium changed over time, we asked them how they felt about it at both the beginning and at the end of the trial:
In the beginning, most people found it unpleasant or disgusting (though you will notice there is still one “very delicious” rating!), but:
By the end, a majority found it either neutral or pleasant, though many people still found it super gross.
You might expect that potassium enjoyment would be related to weight loss, but we didn’t find much evidence for that. We didn’t notice any statistically significant relationships with weight loss, though looking at the plots does seem suggestive:
So it’s possible that people who enjoy potassium salts are more likely to lose weight by eating them, but if so, the effect is probably too small to detect in this study.
The lithium hypothesis is the only theory of obesity that predicts that straight potassium might help people lose weight. It’s not a very strong prediction, we simply noticed that lithium and potassium are both monovalent cations, and that they appear to have some interaction in the brain, where the lipostat is located. But other theories wouldn’t predict a relationship between potassium and weight loss at all.
Lithium … is an alkali metal ion that appears to affect the brain. Other alkali metal ions like sodium and potassium also play an important role in the brain, and there’s evidence that these ions may compete with each other, or at least interact, in interesting ways (see also here, here, and here). If lithium causes obesity, it may do so by messing with sodium or potassium signaling (or maybe calcium) in the brain, so changing the amount of these ions you consume, or their ratios, might help stop it.
However, the results of this study are not conclusive evidence in favor of the lithium hypothesis, and it benefits us to explore some alternative explanations.
Prosaic explanations like “potassium caused people to lose water weight” would seem to be ruled out by the fact that many people’s appetites got noticeably weaker, and the fact that some people mentioned that they had never lost weight so quickly or easily before. Same thing for placebo.
So the two classes of likely alternatives are that either it’s something confounded with the potassium dose (i.e. when you take more potassium, you also do more X), or that potassium causes weight loss for some other reason than its relationship to lithium.
A natural starting point is to consider whether obesity could be just another disease of deficiency, one you develop if you don’t get enough potassium. Scurvy is the disease that happens when you don’t get enough vitamin C, beriberi is the disease that happens when you don’t get enough vitamin B1, could obesity be as simple as a potassium deficiency?
Unfortunately we think that is not the case. Diseases of deficiency are easy to identify because they regularly crop up in situations where people eat a limited diet for a long time. Both beriberi and scurvy, for example, were common among sailors on long voyages.
Obesity does not really fit this profile. People today may not be getting enough potassium, but if obesity were a disease of deficiency, you would expect to see it showing up in historical records of cities under long sieges, sailors on long voyages, explorers in the Antarctic, and so on.
We see two distant ways to reconcile this idea, however. The first would be if potassium deficiency causes obesity, but only over the very long term. For example, maybe you only develop obesity if you eat a low-potassium diet for 10 years. This would be unusual and we think it is unlikely, but it’s consistent with the data.
The other is if obesity occurs in the rare cases when people both have a potassium deficiency AND have lots of access to calories. Sailors, explorers, and other people who tend to get diseases of deficiency usually are not eating that well in general. Maybe obesity is only triggered when you’re not getting enough potassium, but you can otherwise eat as much as you want. We think this also seems unlikely, but again, we can’t rule it out.
Hydration / Clearance
People drank a lot more water on the potassium trial because the potassium salt made them thirsty, and they had to pee a lot. People also drank a lot of water on the potato diet, for similar reasons. Is it possible that both diets cause weight loss because they encourage you to drink huge amounts of water, and that water flushes your system (or something)?
This seems pretty unlikely to us, though it is consistent with all the evidence. If someone wants to try the super-hydration community trial, where you try to drink 5 liters a day or something (don’t use that number we made it up, figure out what is actually safe), that would be fairly interesting. We don’t expect it would cause comparable weight loss, in part because we think someone would have noticed by now if staying hydrated was enough to cure obesity. But it sure would be interesting if it did!
Potassium and sodium balance each other in biological functions. To regulate the increased amount of potassium they were consuming, we encouraged people to consume more sodium as well, and they may also have naturally craved more sodium as they ate more potassium.
As a result, people on the potassium trial may have been getting more sodium than normal. For similar reasons, people on the potato diet may have been getting more sodium than normal. So one kind of weird possibility is that sodium is what’s causing the weight loss here, not potassium.
We did have this in mind from the start, so one of the bonus variables for the study was estimated daily sodium intake.
Unfortunately, out of the 233 people who entered data, only 20 people tracked their sodium, so we don’t have much evidence. But what evidence we do have doesn’t support this interpretation. People who consumed more sodium actually ended up with higher weights at the end (r = 0.101), though the relationship is not significant (p = .670).
In general we do not expect that sodium is responsible for the weight loss observed in this study, nor would we encourage anyone to try a high-sodium diet. But again, we can’t really rule it out.
Is it possible that potassium increases the clearance of something other than lithium? Just making more urine will increase the clearance of some things! Or could it treat obesity in some other way?
It seems likely, but we can’t really be much more specific than that. Potassium has approximately one zillion roles in biology, so for example if obesity is caused by anything to do with “hormone secretion and action”, which seems like a pretty broad category, potassium could potentially be a treatment. This seems like a question for someone who knows more about biochemistry than we do.
8. Future Studies
There are a number of studies that could be run to get more information. We might run some of them ourselves in the future. For now, here they are as brief sketches.
We know that one of the biggest criticisms we’re going to get on this study is about the lack of blinding and lack of a control group. Everyone in this study took potassium, and everyone knew exactly what they were taking.
Let’s imagine what a control group might look like. It’s well-established that people get heavier as they get older, so over the course of 29 days, people who do nothing should on average end up weighing slightly more by the end. We’re pretty sure that a straight control group would have lost about 0 lbs and maybe would have gained some small fraction of a pound over the course of the study — if you gain 2 lbs a year, that’s about 0.17 lbs a month.
But it’s true that people in this study were paying more attention to their weight and to their diet, and it’s possible if they were taking packets of some other white powder that wasn’t potassium, they would lose weight for some other reason. It’s possible that there’s some level of placebo.
That’s fine, because this study was never intended to be the final word. It’s the first study, not the last.
While the hierarchy of evidence is very important, a meta-analysis of multiple randomized controlled trials doesn’t just happen overnight. With this study, we’ve shown that it’s plausible that potassium by itself could lead to weight loss. There wasn’t evidence for that before.
But now that we have this evidence, it might be worth investing more time and energy in a more controlled or more complex study.
We wouldn’t want to do a straight control group where people do nothing, because that would reduce our effective sample size and it would be boring for participants. Fortunately, there are designs that can help with both problems. Here are two ideas:
First of all, we could run a crossover trial. In this case, the study would run for two months. One half of the participants would be assigned to take potassium for the first month and then take no potassium for the second month. The other half of the participants would be assigned to take no potassium for the first month, and yes potassium for the second month. This allows both groups to serve as controls without reducing our sample size.
Another idea would be to run a dose-dependent experiment. The design might look something like this: one half of the participants would be assigned to a protocol that involves them working up to a dose of 2000 mg of potassium a day. The other half of the participants would be assigned to a protocol that involves them working up to a dose of 4000 mg of potassium a day. (You could also do a dose-dependent experiment with more conditions — some people assigned to 1000 mg a day, some to 2000 mg/day, some to 3000 mg/day, etc.) If potassium is the active ingredient, you should see more weight loss in the group(s) assigned to the higher dose(s).
Comparing different doses allows us to have a control group without having to have a “no treatment” group that spends the month doing nothing. Both groups are providing valuable data, and we still control for the effect of the intervention. It isn’t blinded, but this design guards against placebo effects because it would be hard for the people in the 4000 mg/day group to arrange to lose more weight than the 2000 mg/day group.
The main issue in both cases is statistical power. You might need very large sample sizes to detect these differences, and no one should run one of these studies without conducting a very careful power analysis. But, the designs are theoretically sound.
Other Diet(s) High in Potassium
Potatoes are very high in potassium, but they are not the only food that is very high in potassium. Other foods that are very high in potassium include lima beans, swiss chard, spinach, bamboo shoots, butternut squash, kohlrabi, portabella mushrooms, white beans, bok choy, and many others (though avocado and banana are maybe overrated as sources of potassium!).
If the potato diet causes weight loss because it’s high in potassium, a non-potato diet that is high in potassium might also cause weight loss. So one thing you could do is arrange a trial of some other high-potassium diet and see if that also caused weight loss.
This isn’t a sure thing, however. Other foods do contain potassium, but it’s possible that the potassium is different in these other foods — less bioavailable, released more slowly, part of a different compound, etc. So we don’t think this would be a very strong test of the theory, because it introduces so many new variables.
In addition, we want to note that many of the items on the list of high-potassium foods are foods that we suspect might be high in lithium. In particular, there’s evidence that lithium accumulates in leafy greens, sprouts, and maybe in gourds, which matches most of the foods on the list above. If the potato diet works because it’s high in potassium AND low in lithium, these other high-potassium foods might not have any effect at all.
If we had to pick just one high-K food to test, we would probably pick coconut water. It’s a liquid, so the potassium is probably more available than average. It’s relatively high in potassium, with about 600 mg per cup. It’s easy to find and requires no preparation. And (as far as we know at least) coconut water isn’t swimming with lithium. So if people wanted to try getting 2000+ mg per day of potassium from coconut water, that would be pretty interesting.
Low-Potassium Potato Diet
In the course of designing this study, we came across a set of practices used to remove potassium from potatoes. Some people with serious kidney disease have to avoid consuming too much potassium, and these techniques were developed so they could enjoy potatoes safely. Potassium removal is usually accomplished by slicing or dicing the potatoes in small pieces to increase surface area, and then soaking (before and/or after cooking) or boiling them in water to leach out the potassium (e.g.: link, link). Some sources claim that this can remove more than 50% or even up to 70% of the potassium in potatoes.
We could test these techniques by preparing some potatoes with these methods and sending the potatoes (and the water they were soaked/boiled in, which should contain the removed potassium) to a lab for analysis. If the sliced/boiled/soaked potatoes had much less potassium than potatoes that were baked or roasted or something, that would suggest that these techniques remove potassium as advertised.
We could then use this information to do another test of the weight-loss powers of potassium, by running an experiment with a modified form of the potato diet.
One group would be assigned to eat a potato diet with potatoes prepared in a way that preservesas much potassium as possible (probably baked), and the other group would be assigned to eat a potato diet with potatoes prepared in a way that removesas much potassium as possible (probably boiled and then soaked and then fried). If the preserves-potassium group lost a lot more weight on their potato diet than the removes-potassium group, that would be further strong evidence that potassium is the main active ingredient in the potato diet.
This prediction matches the following tidbit from M’s experience with the potatoes-by-default diet, which makes it seem somewhat more more plausible: “I seemed to be able to eat much more when the potatoes were sliced/grated (e.g. Swiss rosti, Chinese tudousi) than when they were closer to whole potatoes (i.e. diced, potato wedges, etc.). I’m not sure why.”
Some people think that the potato diet works because it is a mono diet. It cuts out most other foods, so there’s very little variety, and some people (e.g. here) think that food variety is part of what makes people gain weight. But if soaking all the potassium out of potatoes made for a much smaller effect, that would mean there was a big difference in weight loss between two otherwise-identical mono diets, which would be hard for food variety to explain.
Potato Diet with Urine Test
One plausible hypothesis is that potassium helps clear lithium from your brain, and this is why it causes weight loss.
If this were the case, most of the lithium that is cleared from the brain should end up in your urine (urinary lithium seems to be a good proxy for levels in the body in general). It should be possible to test people’s urine for a while to establish a baseline, and then start them on the potato diet and see what happens. The level of potassium in their urine should increase dramatically, since there is so much potassium in potatoes. It would be interesting to see if the level of lithium in their urine increased as well.
If urinary potassium levels were correlated with weight loss, that would be more evidence that potassium is the active ingredient (though they might not be correlated, since urinary potassium levels are part of a control system). If urinary potassium levels were correlated with urinary lithium levels, that would be more evidence that potassium is forcing lithium out of your brain (or some other reservoir). And if urinary lithium levels were correlated with weight loss (or frankly, even if they just went up when you started the potato diet), that would be strong evidence in favor of the idea that lithium is the cause of the obesity epidemic.
This could be the smoking gun for the lithium hypothesis, which makes it a pretty attractive idea. The problem is that we don’t have any experience running studies with urine samples, so we’re not sure how to design this study or how to run it. We’re also not sure whether it’s possible to run it over the internet, or if we would have to get a bunch of people together in person. If you do have experience in running studies with urine samples, and you’re interested in helping, please contact us.
However, even this study might not be conclusive. It’s possible that potassium counteracts the effects of lithium but doesn’t increase the rate of clearance. For example, potassium might compete with lithium in the brain without forcing it out. It might reduce lithium absorption in the small intestine. It might keep lithium from leaching out of your bones. It might do something else. (Lithium pharmacodynamics remain poorly understood.) So while it’s plausible that potassium increases lithium clearance, we aren’t confident that’s how things work.
We ran this study because we suspected that potassium might be the active ingredient in the potato diet, that the high levels of potassium found in potatoes might be why a diet high in potatoes causes weight loss. These results support that interpretation.
The weight loss observed in this trial was small on average, but the doses of potassium were intentionally very low. There’s evidence that the relationship between weight loss and potassium consumption is dose-dependent, such that people who took larger doses lost more weight on average. Regression modeling suggests that someone who was consuming a dose of potassium equal to the amount provided by the potato diet would lose a similar amount of weight as people lost on the potato diet.
These results are not decisive. Indeed, no results ever are. However, given the small doses involved, the results could not be more strongly consistent with the potassium hypothesis.
Potassium supplementation is scientifically valuable because it’s relatively controlled. But it’s not very practical, because it’s not clear if large doses of straight potassium salt are safe for most people, and because many people find potassium salt really gross. We strongly recommend that anyone who wants to lose weight should do the potato diet instead. The potato diet gives a much higher effective dose of potassium while probably being a lot safer, and may have other benefits.
The all-potato diet is a relatively big commitment (though much easier than most people expect), so you may prefer to try the half-tato diet instead. This involves getting about 50% of your calories from potatoes and, based on the available case studies, seems to be more than 50% as effective and much less annoying. We plan to study it more soon.
If for some reason the potato diet doesn’t work, we would recommend you try to find some other way to eat a diet that’s exceptionally high in potassium.
If none of these things work for you, then you can try direct potassium supplementation, though you should consult with your doctor, definitely not do it if you have diabetes or kidney disease of any kind, and limit yourself to no more than 5000 mg a day.
We probably will not follow up on this study at 6 months and 1 year, since the average weight loss was so small. It seems unlikely that 0.89 lbs of weight loss will be statistically detectable several months later.
However, several people reported that they are planning to stay on the potassium longer-term, so we may have more results soon from the people who reach 60 days on low-dose potassium.
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Thanks for going on this journey with us.
Sincerely, Your friendly neighborhood mad scientists, SLIME MOLD TIME MOLD
APPENDIX A: Delivery
People overwhelmingly took potassium chloride (93.3%), overwhelmingly as a salt (92.3%), and mostly as the brand Nu-Salt (62.9%). The most popular method of delivery was to take it dissolved in water, juice, a sports drink, or some other beverage.
We didn’t detect any differences in weight loss for any of these variables, but given that almost everyone took the same kind of potassium in roughly the same way, we wouldn’t have the statistical power to detect any differences unless they were really huge. So there may be differences, but we wouldn’t expect to see any evidence for them in this data, and indeed we do not.
However, the delivery method does seem to make a difference in terms of enjoyment. Here is a sample of people’s recommendations:
(45454797) The metallic taste went away after just a few days and I found the salt to actually taste good with a little apple cider vinegar and water. Gatorade without the sugar! (and easier than pressing lemons all the time)
(40941749) I highly recommend orange fanta if you’re gonna drink your magic potion, and hash browns if you wanna eat it.
(77174810) Yes, KCl tastes gross/weird/bad. I tried a few different concentrations and mixtures with food (don’t mix with a bite of guacamole – yuck!). What I discovered was that mixing it with Simply Strawberry Lemonade makes it very palatable! I dissolved the KCl and a little sea-salt in about 1 oz of water. Then added about 4-6 oz strawberry lemonade. You could damn near sip it this way! Apple cider was the second best mixer.
(94352426) Higher concentrations were only drinkable to me in carbonated drinks made it okay to drink. For me this was the biggest limiting factor, always having to have carbonated water in home, buying it every time I went grocery shopping those bottles are a lot of extra weight.
Though there was considerable variation:
(52533228) By far, the easiest way for me to integrate it into my routine was to add it as a salt substitute in my cooking or meal prep. I could not stand adding it to drinks – the taste was usually awful and harsh. When it was added to food, the flavors mixed well in general and it was much much less noticeable.
(79332762) In terms of taking the potassium, I really disliked it. I would happily take a pill 1-2x per day, but I really dislike the taste of KCL. I tried two approaches to taking it, mustard & lemonade. With mustard it worked ok for low doses (1/8 tsp) but for larger doses it felt like too much salt hitting my stomach at once. With lemonade I don’t want to routinely drink enough lemonade that fully masks the flavor. I also really like lemonade as a treat so making it a daily routine (& making it taste bad) felt weird. I don’t really want to chug powerade/gatorade either.
APPENDIX B: Regulated Success
The body puts in a lot of effort to make sure you don’t get too much potassium. So one thing you might expect to see on this trial is that people start losing weight at first, but as their body acclimates to the extra potassium and their kidneys start filtering it out more aggressively, they stop losing weight and they maybe even gain back the weight that they lost.
Some people did mention something along these lines. For example, participant 98856740 (who submitted after Dec 1 and whose comments are therefore not in the main dataset):
I lost 6 pounds in the first week and then didn’t lose any more. In fact I bounced between that low number and about three pounds higher. During that weight loss period, I felt hot, enough to wake me up at night. I’ve heard people describe hot flashes during menopause that way. Once I got to the plateau stage, I no longer felt hot, just normal. I speculate that my metabolism was using heat to lose weight. I have no idea why it stopped. I don’t think there was anything materially different about the early days.
From the data, we’re not sure what to think. On the one hand, there are very few clear reversals. For example, the number of people who dropped 5 lbs at some point but ended up losing no more than one pound by day 29 is two, specifically these two participants:
But on the other hand, most people hit their minimum weight well before the last week of the study, suggesting that many people hit a plateau early on. Here’s the plot where we highlight each person’s day of minimum weight:
You can see that some people did hit a relatively low minimum weight early on and then never go down further from there. This may be evidence that some people hit a plateau.
APPENDIX C: Accounts of Greatest Weight Loss
Well, my time in the experiment has been shocking, to say the least of it. So obviously I’m morbidly obese so I should probably address that right away considering I’ve lost over 12 lbs during this experiment.
In January 2022, I started working with a doctor that specializes in weight loss. I was put on a low-carb, ketogenic diet 6 days per week with 1 day of free eating anything I wanted, and an exercise routine of moderate walking every other day. My starting weight was ~485 lbs. My compliance with the diet and exercise routine was 100% from January until the start of the potassium trial. My starting weight at the beginning of the trial was 476.2 lbs, so I lost approximately 9 lbs during that 9-month time frame.
I DID NOT change my diet or exercise habits during the trial to any appreciable measure. There were a couple of times I mixed up my exercise routine but mostly I stuck to the same 60 minutes on a treadmill every other day. Any changes to the exercise were noted in the sheet.
Overall I think it’s incredible that the simple change of adding potassium seems to be responsible for a sudden change in the rate at which I was able to lose weight. I will be continuing supplementing potassium going forward, this is the single most amount of progress I’ve made in weight loss in a month.
I’m going to try to think of anything I can disclose here to give context to the data.
Potassium was consumed from Nu-salt and mixed with a Gatorade zero powder that also had some potassium (both details recorded on the sheet). I didn’t have any set schedule for the potassium, I simply added it whenever I felt thirsty and acquired water (up to the dose limit for the day)
My diet was a strict ketogenic diet (under 20 grams total carbohydrates per day, gross carbs, not net) for 6 days per week and one day a week of eating anything I wanted. I do not track calories. I don’t track macros other than the number of carbohydrates consumed to stay under 20. The 20-carb limit includes the 2g carb per serving of the Gatorade zero powder I used to mix the nu-salt.
I weighed myself completely naked on an “Ideaworks JB5824 Extra Wide Talking Scale” between 8:30 and 9:00 AM every day, preferably after having a morning bowel movement. If I didn’t have one, I would still record my weight. I made a note on the sheet whether or not I had a bowel movement for that particular day.
My heart rate was tracked using an AmazFit band with the pulse check feature, typically immediately before or immediately after weighing myself in the mornings.
Sleep is highly subjective but overall I think my sleep quality improved during the experiment, generally sleeping longer without waking up in the middle of the night.
My mood and energy have been nothing short of fantastic. On a normal day pre-trial, I’d rate my average mood and energy levels in the 4/5 area on the 1-7 scale. Somewhere during week 2 of the trial, I really noticed how elevated I felt in my mood all day long and generally my energy levels were high regardless of the amount of sleep.
During the first week of the experiment I remembered to measure my waist circumference as per the CDC method but frankly, I forgot to do that, but I have included a final measurement.
A final note about compounding factors: lithium reduction
I first discovered Slime Mold Time Mold through the “A Chemical Hunger” series of blog posts, but in particular, the section covering lithium is what caught my attention for potential causes of obesity. The reason it caught my attention is I was put on lithium to treat a neurological condition that I was diagnosed with (tourette’s syndrome) when I was 7 years old, and I can positively say that was the time when I began to put on weight steadily over years and decades regardless of my diet and exercise habits. I am 36 years old and have been off lithium for over 10 years now, but the lithium article really resonated with me as a potential cause. So I’ve installed activated carbon and reverse osmosis water filtration systems on all of the water taps in my house since the first lithium post in 2021. The filters I’m using the claim to remove “over 90%” of lithium from water. (City of Cincinnati water, Cincinnati, OH)
So I don’t know how entirely relevant all that could be to the data, but all of the water that I was mixing the potassium in was also water being treated for the removal of lithium specifically (although its been approximately a year of running filtered taps and only the addition of the potassium has resulted in dramatic weight loss)
I did not participate in the potato diet trial.
Anyone that wants to supplement potassium with Nu-salt should try mixing it with the Gatorade zero powder, it almost completely covers the taste and made the trial a breeze.
One last thing, I chose to limit the amount of Nu-salt I was consuming at the 1300mg per serving mark just because I didn’t want to go through my supply of Nu-salt and Gatorade zero powder too quickly. I felt entirely fine with the amount I was consuming and believe I could have easily continued in either increasing to higher doses or adding more 1300mg doses throughout the day.
Well, I feel like I’m rambling at this point but if there are any questions please feel free to ask, in the meantime I’m going to continue supplementing with potassium.
First I just wanted to clarify that I have been following a Time Restricted Eating, or Intermittent Fasting plan since Sep 30th, prior to learning about this study. I was excited to join the study since I found your posts on Twitter talking about the potato diet that people have raved about. I’ve been eating my meals between 12pm and 6pm every day and I’m sure it has contributed significantly to my weight loss. I hope this doesn’t skew the study results too much as a result of my eating schedule.
I did focus on keeping my calories under 3000 per day with a target of 2500. I also made an effort to exercise 2 to 3 times per week of 30 mins or more. That being said, I do think the potassium helped me manage my hunger, and specifically I felt like I didn’t need to eat that much during the day to feel full.
I found the study relatively easy to do. I set reminders for each dose through out the day, as well as a reminder for recording my weight and waist measurements and used an app to track those using my smart scale and smart measuring tape, both from Renpho. I discovered that drinking each dose with straight water was the easiest and fastest way to get it down. I tried with other drinks and things, but I just knew going in that it would taste funny, and got it over with quickly each time.
Starting out I didn’t have an 1/8th teaspoon measure, so I just started with 1/4 teaspoon. Being 6’4″ and 300 lbs, I figured I could handle a larger dose to begin with. Then as a result of not paying attention to the instructions very well, I ended up going up pretty quickly in dosage the first two weeks. For side effects, it was noticeable the first few days where I felt some stomach discomfort, and general unease, but it went away after the first week. The only other side effect that I think was related to the potassium, is that I found I had to pee a lot more often depending on how much water I was drinking. I tried to drink a lot of water throughout the day so I could get the most out of my bowel movements, but one issue was I just had to go pee a lot more. It felt like I would drink a cup of water, and then 20 mins later have to pee like I hadn’t gone all day. 🙂 I would say I had 1 to 2 liters of water per day in addition to meal time drinks (milk, juice, diet soda). I’m going to continue my eating and exercise schedule, but will stop taking potassium and just record my stats each day for the next month. I’d like to really see how the weight loss was impacted by the potassium. I’ll keep updating the spreadsheet and see how things go. I’m happy to talk more about my experience or answer any questions as part of any follow-up.
My 4 weeks are done, although I intend to keep taking potassium given the moderate success I experienced. Taking the potassium was very easy (with the exception of the few times I put nu-salt into pill casings and took it that way – this caused stomach pain, which I did not experience when just taking it dissolved in liquid). My overall impression is that potassium acts as a mild appetite suppressant. Thanks for running this trial, I’m looking forward to reading about the compiled results.
Sorry for the delay- I couldn’t load the sheets properly on my phone, but I was keeping track and am just now getting the chance to fill out the last week. Please excuse the order of the train-of-thought below.
I took my last weight the morning of Thanksgiving and proceeded to eat my weight in food. I haven’t been eating fast food lately but the cravings hit me hard (probably from a combination of eating way too much, alcohol, and not supplementing for a couple of days). My plan for now is to finish up leftovers today, grab some fast food over the next couple of days, and probably restart a 30 day period on Wednesday having gained about 5 pounds in a week.
All of my supplementary data (heart rate, sleep, exercise) was from my fitbit.
It was very true that I didn’t think of food while doing the trial. At the lower doses, my hunger was affected but my appetite was not. At the higher doses, both were affected.
The biggest struggle for me was trying to keep track of my calories. I feel like it negatively impacted my trial because it did affect what I ate, even though I was supposed to eat whatever I wanted. I would eat what I wanted and feel shame/guilt for eating over X amount of calories (arbitrary number from back in my restriction days). The perhaps more interesting way it affected the trial was, once my appetite started being affected by supplementing, I would finish meals that I wouldn’t have because “I had already tracked the calories for it, I should get it,” “how can I track 1/3 of a meal,” etc. For my second attempt at the trial I will not be tracking calories, and hopefully not have the pressure of numbers to affect my eating habits. I understand that it was an optional variable anyways, but hypothetically the change in weight would reflect the appx input anyways.
I did not look into the lithium correlation at all, but if it is important- for meat markers, I only eat white meat. For egg markers, I only eat egg whites. The only thing I noticed that seemed to give me actual hunger pangs was if I drank a significant (about or more than 24 oz in a sitting) diet soda. Of course you can see in my data that alcohol also ruined a couple of days, but that didn’t actually make me feel any more hungry, just more crave-y and less likely to resist eating an entire pizza (apparently).
My work schedule is Fri/Sat nights, Sun-Tues mornings, and a random overtime on either Wed or Thur. Although my Fri shift is the same every week, there is a huge difference between that 3pm-11pm shift and my Tues 530-130 shift in terms of when and what I typically eat (and my sleep schedule).
There was a huge difference in my general desire for food if I took the supplement in the morning before eating. If I took my first dose with food, I would be thinking about food sooner (though I wouldn’t say it was every hunger, just craving). When I took only the supplement and then went to work, it was almost always that I wouldn’t think of food until after work. If I took a dose without food and then went on my walk, even if I had already eaten that day, I would feel very light-headed.
I’m happy I found out about this trial. I am generally pleased with the outcome, if not the methods I specifically used, and am more excited about starting next week with a little less restriction. I’ll still track in case the data is useful for you, but probably only the weight and doses.
[SMTM’s note: despite the comment below, this participant reported losing 8.6 lbs.]
Thanks for running this trial, it was interesting. My subjective feeling is that the potassium supplementation had no discernable effect on my brain function, hunger/diet, or weight. I’m planning to continue supplementing potassium though because my food diary shows my intake of it was very low and I’m curious whether it might have any longer term effects past just the first 4 weeks.
First of all – holy shit! It’s amazing how well this worked and it’s also surprising that it’s never really been studied before! Thank you for the analysis and thought that you put into this. For this trial, I basically just ate whatever I felt like, went to a football tailgate party nearly every weekend with lots of beer and foods you would not associate with dieting… and still lost nearly 10 lbs! I plan to continue on for at least another couple months so feel free to follow up later if you want to.
Interestingly, I was born and raised in Colorado. I lived there for my first 30 years until 2003 when we moved to the East coast and although I am a bigger person (6’5″/225 in 2003), I was never really “heavy” until maybe 2010 or so. I kept putting on weight as I aged into and past my 30s and I just followed conventional “wisdom” that it was due to getting older. Each year I would have a few extra pounds.
I have tried every diet/exercise and variation of CICO, atkins, keto, IF, etc., etc., etc. to try and lose weight. To no one’s surprise, nothing really worked for long and the weight always came back. At the end of 2020 I was over 275. It took me three months of busting my ass to lose 20 pounds and as soon as I started eating “normally” again, I slowly started putting weight back on.
Anyway, you may have just solved obesity. I hope you enjoy being billionaires. Don’t forget us little guys that did nothing but participate in your study when you are trying to decide on the color for your private jet (I think dark blue would be nice).
Notes and observations:
Yes, KCl tastes gross/weird/bad. I tried a few different concentrations and mixtures with food (don’t mix with a bite of guacamole – yuck!). What I discovered was that mixing it with Simply Strawberry Lemonade makes it very palatable! I dissolved the KCl and a little sea-salt in about 1 oz of water. Then added about 4-6 oz strawberry lemonade. You could damn near sip it this way! Apple cider was the second best mixer.
I felt thirsty a LOT of the time, especially in the first week or so. I increased my water consumption by over a quart/day for the duration of the study (still ongoing)
On the weekends, I ate poorly (nutrition wise) but still overall was eating way less than I usually did.
I only tried a 1320mg dose once. I didn’t feel great but cannot say for sure that it was that higher dose. I plan to try two higher doses/day for the second month
I settled on 3 doses of ~990mg (3/8 teaspoon) a day at 0730, 1130, 1600. I felt like this kept hunger at the lowest level overall and was easy to stick with.
I found that if I took the supplement when I was already hungry, I’d eat more overall. So I take the dose an hour or so before I’d normally eat a meal.
I’m very curious about this mechanism for weight loss. Does K+ just act as an appetite suppressant? Or is it more that the lipostat is turned down and that makes you less hungry? If lithium passes through the body fairly rapidly, how long does the effect last on the brain (if that is what is happening)? When I have cut calories in the past, it was an uphill battle to fight hunger. Presumably my lipostat was set too high so I’d be hungry and also not lose weight effectively because my body was not trying to lose weight. Hmm, might make sense… I plan to do this for at least another month if not two. It will be interesting to find out:
Could there be any detrimental long-term effects of taking this much extra K?
If I stopped the supplemental K, will I start to trend back up in weight? How hard will it be to keep the weight off?
How long does the effect last? Will I be (normal) hungry tomorrow if I stop supplements today?
I intend to experiment with the following after I hit my target:
Could I take the supplement every other day or once a week as a “maintenance” dose and keep the weight off? Or maybe just a smaller daily dose? Looking forward to your further analysis and trial results.
Drugs have effects. Take more of a drug, and you’ll get more and bigger effects. They call this a dose-response relationship — take some dose, get some response. Benadryl makes you drowsy, mercury gives you hallucinations, cyanide kills you.
But these effects only kick in above certain doses. At very low doses, the drug has no effects. This always has to be true, because at zero dose, the drug can’t have any effects.
Then at some dose, the effect starts kicking in. Sometimes this means you start feeling it a little and it gets stronger over time. Other times, it means the response rate increases, and more people start feeling the effect as they take bigger doses.
At some point, the effect is as strong as it can possibly get and it doesn’t get any stronger. Everyone who is going to have a reaction is getting the strongest effect they can get.
Dose-response relationships can be described with dose-response curves, like this one:
Often these curves make the most sense on a log scale (probably because this is bounded exponential growth; it’s exponential but eventually everyone who is going to have the effect already has it), so for this exercise, we’ll be portraying the x-axis on a log scale. This may not be true for all drugs, but it’s a reasonable starting place.
Lithium is a metal that is also a drug that sometimes causes weight gain. But no one really knows what the dose-response curve for weight gain on lithium looks like. Weight gain is clearly a side effect of clinical doses of lithium (about 50-300 mg of elemental lithium a day), at least for some people. But almost no one has studied lithium doses below 50 mg a day, so we don’t know at what point this weight gain effect starts kicking in.
The dose-response curve could look like this, where weight gain doesn’t show up until you hit therapeutic doses of 100 mg/day and more:
Or it could look like this, where effects kick in starting at subclinical doses of as low as 1 mg/day:
Or it could even look like this, where weight gain starts at trace doses of less than 1 mg/day, and once you’re getting 10 mg/day, you’re maxed out:
The curve could be spread out, with gradual effects increasing across all plausible doses:
Or it could be incredibly abrupt, where weight gain happens suddenly once you’ve passed a certain threshold:
There’s also good reason to believe the dose-response curve will be different for different people. The response may be different in terms of the shape of the curve, when the effects kick in, and when they max out.
By ancient tradition, we will call our example patients “Alice” and “Bob”. In this hypothetical, Bob starts seeing weight gain as he approaches 1 mg/day and has already gained almost 40 lbs at 10 mg/day, but Alice doesn’t get the same effects until noticeably higher doses:
It might also be different in terms of the maximum effect. In this next example, not only does Alice not start gaining weight until 10 mg/kg, she caps out her weight gain at just over 20 lbs, while Bob gains 40 lbs on a similar dose:
Psychiatric doses of lithium are in the 50-300 mg range (elemental), and some people think this means that weight gain must happen in this range. But this may not be the case.
First of all, there’s plenty of evidence suggesting that the psychiatric effects of lithium kick in at trace doses of less than 1 mg/day. The effects may not be very strong at trace doses, but you can still pick them out in a population-level analysis. In fact, there’s a wholedangliterature finding that rates of dementia, suicide, homicide, and other “behavioral outcomes” are associated with trace lithium levels in drinking water. This suggests that some effects kick in at very small doses.
But regardless of whether or not trace amounts of lithium lower the suicide rate, the fact is that lithium has several different effects, and there’s no reason those effects can’t kick in at different doses. It might look something like this:
(To be clear, all these curves are completely made up for the purposes of illustration.)
This should probably be our default assumption. Most drugs have multiple effects, and different effects often kick in at different doses. For example, alcohol is a drug that makes you talkative at low doses and makes you puke your guts out at high doses.
(Your mileage may vary. Adam Mastroianni, who reviewed this piece, says, “Not me, I puke a tiny amount at tiny doses, increasing to a massive amount of puke at large doses.”)
In fact, we know that lithium has effects that kick in at different doses, because therapeutic effects tend to kick in well before patients die from lithium toxicity, and death is also an effect.
It’s true that some people don’t gain weight at all, even on clinical doses of more than 1000 mg/day. But this might just mean that in their case, the dose-response curve for weight gain is above the dose-response curve for toxicity/death. You can’t get there without dying, so we never see it. (And for some people, the mechanism by which lithium causes weight gain probably just doesn’t work at all.)
In any case, we have almost no information about what the curves might look like for lithium, because there’s very little research on doses below the low end of the clinical range (around 50 mg/day). There’s that literature on trace doses in drinking water which we mentioned above, and there’s one RCT from the ‘90s finding that trace doses of lithium made violent offenders friendlier and happier — but as far as we know, there’s never been any formal study on doses in the range of 1-50 mg/day. If anyone has studied weight gain on lithium doses below 50 mg/day, we’ve certainly never seen it.
So let’s see what we can do to figure out anything at all about the dose-response curve for the weight gain effects of lithium — and, maybe more interesting, the effects of lithium in general. Do any of these curves start showing up at subclinical doses?
One thing that’s interesting, in terms of our bigger “is lithium exposure causing the obesity epidemic?” question, is that most of the side effects of lithium are non-specific — if you feel nauseous and tired, it could be lithium exposure, but it could equally be a million other things. That makes it hard to tell if symptoms of lithium exposure have increased over the past 50 years, since no one has been tracking brain fog rates since 1970. If the rate of increased thirst has dectupled, we might not even know (unless…).
Some of the effects we’re going to study — like fatigue, depression, and muscle weakness — are also symptoms of hypothyroidism. These are also nonspecific, but if they were to increase, they might be diagnosed as hypothyroidism. We’re curious to see if they increase on low, subclinical doses.
The survey was pretty straightforward. First, we asked people for their basic demographic information. Then, we asked them to describe their previous experience with lithium.
We allowed people to record information for up to five different doses of lithium — different in either being different amounts (e.g. 1 mg/day vs 5 mg/day), different compounds (e.g. lithium as lithium orotate vs. as lithium carbonate), or both.
For each dose, we asked people to tell us what compound they took, how much they took per day, and approximately how many days they tried the dose for.
We also asked them what effects they experienced on each dose. Our list of effects was based on this page from Mayo Clinic, though our list did not include all the effects mentioned on this page.
We make no claims that our list is any sort of principled selection — it’s just a subset of effects we decided to include. There were too many to include all of them, so we made some calls.
In particular, we focused on “milder” side effects, since we knew that the nootropics folks would be on lower doses than a clinical population and would probably not experience the more severe effects. We also combined some effects to avoid redundancy — for example, we combined multiple effects related to passing gas into the single effect “flatulence” on our list.
We do regret cutting “fruit-like breath odor” and “eyeballs bulge out of the eye sockets”. Now those are side effects.
In any case, the final list was:
Increased clarity / focus
Confusion, poor memory, or lack of awareness
Fast, pounding, or irregular heartbeat or pulse
Stiffness of the arms or legs
Troubled breathing (especially during hard work or exercise)
Unusual tiredness or weakness
Lack of coordination
Loss of appetite
Ringing in the ears
Bloating or indigestion
Loss in sexual ability, desire, drive, or performance
We also included an option for “other”.
Finally, because we are especially interested in weight changes, we also asked for each dose, “If you lost / gained weight, what was approximately the magnitude of the loss / gain”, with answers in kilograms.
Nootropics enthusiasts often take small amounts of lithium, usually because they believe it has a variety of beneficial effects at low doses, effects including balanced mood and reduced stress. So recruiting from the nootropics subreddit seemed like a good way to find people who already have experience with subclinical doses.
A total of 40 people filled out the survey, providing data on at least one regimented dose (an amount taken daily for a period of time) of lithium. Of these, 20 people also reported on a second dose, 5 reported on a third dose, 2 reported on a fourth dose, and one person reported on a fifth dose. From this we can see that of the respondents, 50% have tried at least two different doses of lithium at some point.
For now, we will ignore that some of these doses are the same people, and just treat these as 68 different individual doses. Going back and doing more complex modeling at some point would be a good idea, we encourage that, but it’s not the focus of the post today. To keep it clear, we will call these “cases”. There are 40 people who gave us 68 cases.
Two people don’t report how much they were taking for their second dose, however, so we will be ignoring these cases. In the end we have 66 cases.
This is all self-report, and we haven’t been at all strict about kicking people out. In fact, we didn’t kick anyone out. Some of the data do look a little strange. One person reported taking 5 mg/day of lithium carbonate, which seems unlikely. But we’re taking the data at face value for now.
First of all, we want to see how much elemental lithium everyone is taking.
Many people reported a single number for their daily lithium dose, but some people reported a range, e.g. “5mg-20mg”. To convert this into a single number for analysis, whenever a person gave a range of values, we went with the average of the range endpoints. In this example, a report of “5mg-20mg” would be converted to 12.5 mg.
Different lithium compounds contain different amounts of elemental lithium. This is the “active ingredient”, so to speak. We did our best to estimate elemental lithium from the numbers people reported. In most cases, this was pretty straightforward. Lithium carbonate is prescribed by the weight of the compound, and the elemental dose is 18.8% of the weight of the listed dose. Lithium orotate usually lists elemental lithium on the packaging, and so most of the time, no conversion is needed.
However, we did have to guess on a few. For example, one person said that they were taking lithium orotate, but said they were taking 130 mg per day. Based on what we know about lithium orotate doses available on the market (see e.g. here), we think 130 mg elemental is very unlikely — this is probably 5 mg elemental, so we coded it as 5 mg. For all these conversions, you should be able to double-check our numbers in the raw data (available on the OSF).
Having made these conversions, we find that people were taking doses between 0.25 and 282 mg per day elemental lithium, over spans ranging from 1 day to 4 years. We use dose per day because it’s easy to track. Here’s the distribution:
As you can see, most people were taking less than 50 mg/day. In fact, most were taking less than 25 mg/day. The median daily dose in this sample is 10 mg/day, the mean is 39.6 mg/day, and the mode (15 people) is 5 mg/day. The next most popular dose after the mode is actually 1 mg/day — 6 people were trying that amount.
In comparison, the average therapeutic dose is 50-300 mg/day elemental lithium, usually delivered as lithium carbonate. So overall, these nootropics folks are taking rather small doses.
Lithium orotate was by far the most popular compound in our sample. This makes a lot of sense — lithium orotate can be purchased over the counter, or over the internet, without a prescription, and comes in relatively low elemental doses, all of which makes it an ideal nootropic. Of the 66 cases, 42 people were taking lithium orotate, 22 were taking lithium carbonate, and one each were taking lithium aspartate and “Lithium Chloride / Ionic Lithium”.
We keep saying “doses”, but it’s important to keep in mind that from a biological point of view, these are not really doses — these are deltas, a change in the daily dose. People are already getting some small daily dose of lithium every day from their food and water, so whatever they are taking as a nootropic is a dose in addition to the dose they were already getting. We don’t currently know what kinds of doses people are getting from food and water — the literature is a little confused at points — but we’re confident that it’s more than zero.
So while we don’t know if the average American is getting 5 mg/day from their food or just 0.05 mg/day, we know they’re getting some amount — for now, let’s call the average everyday dose X. If someone is taking 5 mg/day as a nootropic, they’re not getting a total dose of 5 mg/day, they’re getting X + 5 mg/day.
Let’s start by looking at weight change on these low doses.
Like the doses themselves, weight change was also reported as a range in a few cases. Like the doses, whenever someone gave a range, we took the mean of that range as our point estimate value.
Here are the weight changes people reported compared to the daily elemental dose they were taking. Note that the weight changes here are in kilograms:
That plot is a little hard to read because most people are taking low doses (< 50 mg/day) so most of the points are crammed in over on the left side. To make it easier to read, here’s the same plot with the x-axis log10 transformed (with some jitter in the x-axis to keep points from overlapping):
One caveat is that these plots include many people who didn’t actually mention any weight change at all. Since they didn’t mention it, we assumed the weight change on their dose was effectively zero. This seems like a pretty safe assumption, but just in case, here’s the same plot with only the people who explicitly said something about their weight change:
Most people didn’t see any weight change, or at least, they didn’t report any. But 8 of the 66 cases did report some weight change.
The first weight change reported is a loss of 3 kg, at a dose of 5 mg/day. This is a low dose, and it’s weight lost, not weight gained, which makes it something of an outlier.
The first weight gain reported is an increase of 5 kg on 20 mg/day, which this participant reported taking for approximately 365 days. The next weight gain is 8 kg on 50 mg/day, which the person reported taking for only 60 days.
After 50 mg, weight gain seems to be more common, though certainly not universal. Of people who took more than 50 mg/day elemental, 6 of 18 reported weight gain, which is 33%. The highest weight gain reported was 35 kg (not pounds, he was quite clear) on 56.4 mg/day elemental taken as 300 mg/day lithium carbonate, over 4 years.
So, keeping the limitations of the small sample in mind, this suggests that the weight gain effects kick in around the range of 20–50 mg/day of elemental lithium, for somewhere in the ballpark of one third of people.
The sample size is quite small, but if you squint, it does kind of look like weight gain kicks in a bit earlier for Lithium Orotate than for Lithium Carbonate. We didn’t expect this, but while we were working on this project, a reader pointed us to a small literature finding that lithium orotate is sometimes effective at a lower dose than lithium carbonate.
This is a literature that currently seems to be driven by Anthony Pacholko and Lane Bekar, two Canadian researchers from Saskatchewan, building off of the work of Hans Nieper in the 1970s. In the interest of full disclosure, we should tell you that Wikipedia describes Nieper as “a controversial German alternative medicine practitioner” whose therapies have “been discredited as ineffective and unsafe.” The “see also” links at the bottom of his page are “List of unproven and disproven cancer treatments” and “Quackery”. Caveat lector.
In any case, there is a review by Pacholko and Bekar from 2021, which does cite many sources outside Nieper, and says in the abstract, “[lithium orotate] is proposed to cross the blood–brain barrier and enter cells more readily than [lithium carbonate], which will theoretically allow for reduced dosage requirements and ameliorated toxicity concerns”. They also have an empirical study published in 2022, which reports benefits of lithium orotate over lithium carbonate in mice.
We’re not going to review the whole literature here, but it’s worth noting. Let’s mark it down for now as suggestive.
Weight gain is not the only effect of lithium. It might not even be the most interesting effect.
The nootropics people on reddit dragged us for mostly including negative effects — which, you know what, totally fair. We should have included more positive effects. We’re interested in seeing when the bad stuff kicks in, but while we were at it, we should have looked at when everything kicked in. If we study this again, we’ll include more positive effects.
We also now realize that we should have asked for the effects on a scale (1-7, 0-3, something like that). Asking just “did you experience increased thirst or not” gives us very little information for most of these symptoms. If we study this again, we’ll use more detailed measures.
But for now, let’s look at the data we have. And the data we have are already pretty interesting. People reported experiencing all sorts of effects:
And, to our surprise, they reported lots of these effects even on pretty low doses:
As before, this is a little hard to read because of the squashing. Here’s the same thing with the x-axis log10 transformed:
Even below 10 mg/day elemental (a 1 on the x-axis above, since this is log10), most people are reporting a few of these effects, and some of them are reporting several. Above 10 mg/day elemental, almost everyone reports multiple effects! It’s clear that stuff starts kicking in at pretty small doses.
Moving beyond the aggregated effects, we can ask, what effects popped up specifically? Here’s the list, with the number of cases that mentioned each effect:
Increased clarity / focus: 14
Increased calm: 38
Improved mood: 35
Improved sleep: 23
Trouble sleeping: 7
Confusion, poor memory, or lack of awareness: 12
Fast, pounding, or irregular heartbeat or pulse: 1
Frequent urination: 10
Increased thirst: 11
Slow heartbeat: 0
Stiffness of the arms or legs: 1
Troubled breathing: 2
Unusual tiredness: 5
Brain fog: 13
Eye pain: 2
Vision problems: 1
Lack of coordination: 4
Loss of appetite: 5
Muscle weakness: 2
Ringing in the ears: 3
Slurred speech: 2
Trembling (severe): 3
Bloating or indigestion: 4
Decreased libido: 10
Loss in sexual ability, desire, drive, or performance: 4
Tooth pain: 0
And here are the top 10:
Increased calm: 38
Improved mood: 35
Improved sleep: 23
Increased clarity / focus: 14
Brain fog: 13
Confusion, poor memory, or lack of awareness: 12
Increased thirst: 11
Frequent urination: 10
Decreased libido: 10
We see that the four positive effects are the most commonly reported, which is what we would expect from a population of nootropics users who are taking lithium in search of positive effects. More than half of the cases reported “increased calm” and “improved mood”, and around a third reported “improved sleep”. On top of this, 14 reported “increased clarity / focus”. Of the 66 cases, 50 (about 75%) reported at least one of these four positive effects.
But this also makes it especially striking that so many people reported negative effects. If anything, this population is inclined to downplay the negative effects of lithium, but negative effects were reported quite frequently.
The most commonly reported negative effect was brain fog (13), followed by “confusion, poor memory, or lack of awareness” (12). These sound like the same thing, but there wasn’t perfect overlap. We see that 7 people reported brain fog without reporting confusion, and 6 reported confusion without reporting brain fog.
It’s pretty weird that “increased clarity / focus” is the fourth most common effect and “brain fog” and “confusion, poor memory, or lack of awareness” are effects #5 and #6. Aren’t these polar opposites? Why are they right next to each other in the rankings? Sounds like a possible paradoxical reaction.
The next most common effects were increased thirst (11) and frequent urination (10), which also seem related.
After that, the next most common is decreased libido (10), which is supported by a less common but related effect, “loss in sexual ability, desire, drive, or performance” (4). These are both reported at rather low doses, as low as 1 mg/day.
The next most common are fatigue (8), and trouble sleeping (7), and then we get into numbers too small to go over individually. But even so, almost every symptom we put on our list was reported by at least one person — we certainly did not expect that. The only three symptoms that no one reported were fainting, slow heartbeat, and tooth pain.
Some of these symptoms, like ringing in the ears (3), are only reported by people who were taking more than 50+ mg/day. But lots of effects start appearing at very low doses.
Like with the weight gain, there might be more effects for orotate than for carbonate at the same elemental dose. Don’t take this as conclusive — there’s not all that much evidence. But it is intriguing.
We can even do a regression looking at just the data from cases where people were taking carbonate or orotate. This brings us to a somewhat unusual finding.
When the dose of elemental lithium is used to predict the total number of lithium effects, the regression model finds significant main effects of both dose (p = .0008) and compound (p = .021), and a significant dose-by-compound interaction (p = .0019). The total R-squared is 0.257, which is pretty good. This model suggests that lithium orotate does bring on more effects at a lower dose than lithium carbonate.
But, there is only a main effect of dose (p = .005) when dose of elemental lithium is log10 transformed. In this case, the compound (p = .899) and the interaction (p = .718) are not significant, though the R-squared is pretty similar (0.245).
This difference is pretty clear when we plot both models with their regression lines. Here’s the situation if you don’t log-transform the daily lithium dose. You can clearly see that the slopes of the two lines are very different:
But here’s the situation if you do log-transform the daily lithium dose. You can clearly see that the slopes of the two lines are nearly identical:
This is a little weird. On the one hand, that’s a pretty clear interaction in the non-transformed data. On the other hand, we would expect log transformation to be the appropriate transformation for this analysis. Make of that what you will.
Troof points out that a lot of this interaction seems to be driven by a single participant, who looks kind of unusual and is taking an unusually high dose of lithium orotate. If you look at the plots, you can see them as a somewhat clear outlier (taking the most orotate and having the most effects of anyone on that compound). So probably don’t put too much trust in this data point, and without it, the case for an interaction basically disappears.
These results suggest that many effects of lithium kick in at subclinical levels. In this sample, the majority of people who took at least 1 mg of elemental lithium a day reported at least one effect, and people on doses above 5 mg/day tended to report experiencing several effects.
The most common effects people reported were the four positive effects we asked about, but several negative effects of lithium were commonly reported as well, especially brain fog, “confusion, poor memory, and lack of awareness”, increased thirst, frequent urination, decreased libido, “loss in sexual ability, desire, drive, or performance”, fatigue, and trouble sleeping. A slight majority of cases (53%) reported at least one negative effect.
Weight gain was not a common effect, but it was reported at relatively low doses. The lowest dose for reported weight gain was on a dose of 20 mg/day, and the next lowest was on 50 mg/day. The greatest reported weight gain was on a dose of only 56.4 mg/day. Taken together, this suggests that in the current environment, lithium can cause noticeable weight gain on elemental doses below 50 mg/day, and possibly as low as 20 mg/day.
Unfortunately, this does not tell us all that much about the dose-response curve. There are just too many degrees of freedom, and we don’t know that X value, the amount that people are getting from their food and water. It could be that X is well below the dose-response curve, and +50 mg/day is needed to push you onto the curve:
But it could equally be the case that X is well onto the curve — past the point of greatest sensitivity! — and a big delta like +50 mg/day is needed just to see any weight change at all.
This evidence doesn’t rule anything in, but it does rule some things out. Given these findings, we can mostly rule out the idea that doses below 10 mg/day have no effects. We can also rule out the idea that weight gain starts kicking in at just 0.1 mg/day — it seems pretty clear that you need a bigger delta than that. But we can also mostly rule out the idea that weight gain only occurs above 600 mg/day.
So while it’s good that some things are ruled out, we still don’t know enough to pin down the dose-response curve.
At least, not for weight gain. We do see what looks like evidence of the dose-response curves for other effects.
Troof also played around with the data a bit, and sent us the following graph. The pattern is clear for some effects and rather messy for others, but we see what looks very clearly like the start of a dose-response curve for increased thirst. We also see what look like dose-response curves for improved mood, improved sleep, increased calm, and increased clarity, where rates of the effects increase and then level off. But there isn’t a clear curve for brain fog or confusion, at least not in these data.
One weird thing we noticed is that most of these dose-response curves come down at the highest dose level, suggesting that some of these effects actually get less likely past a certain point. Not sure what’s going on there, we’re interested to hear what people think.
At this point you might be wondering: should someone do a human challenge trial for low-dose lithium? You know, round up some brave souls on the internet, get them all to take 10 mg’s worth of lithium orotate every day for a month, and see what happens to them by the end. Is that a good idea?
We don’t think this is a good idea, for a couple reasons. First of all, we don’t know what X is, which means that increasing the dose by a fixed amount isn’t actually all that informative.
Second, we’re pretty sure that X is different in different places and for different people. Combine this with the fact that different people probably have different dose-response curves for strictly genetic reasons, and the results begin seeming hopelessly complicated.
Finally, while low-dose lithium does seem to have positive effects for many people, some of its effects are quite nasty. We wouldn’t want to subject volunteers to unnecessary brain fog and fatigue. If we were sure that the study would teach us a lot, then maybe it would be worth it, maybe we would be open to convincing people to give it a go. Maybe we would try it ourselves. But since we don’t think it would really answer any of our biggest questions, we don’t think a lithium supplementation study would be worth anyone’s while.
However, Troof has convinced us that there are more than 40 people out there who have already tried subclinical doses of lithium, and that at least some of them will be reading this post. So we’ve put together an updated version of our survey that fixes some of the problems we mentioned above — it asks about the magnitude of each effect, includes more positive effects, and includes more effects in general. If you’ve taken lithium before, you can fill out the survey here, and if we get enough responses, we will post another analysis. If you filled out the first survey, you can fill this one out too, because this one is a little more detailed — just check the box that indicates that you took the first survey, so we can make sure not to double-count you.
Potatoes are special for many many reasons, but by far the most obvious thing that makes them special is that they’re really high in potassium. If potassium is the reason the potato diet makes people lose weight, then there’s a good chance that taking potassium directly would also make people lose weight. Someone should really do a study. Who, us? Ok, fine.
Tl;dr, we’re looking for people to volunteer to supplement small doses of potassium chloride (KCl) for at least four weeks, and to share their data so we can do an analysis. You can sign up below.
Potassium (K) is a slivery-white alkali metal, and element number 19 on the periodic table. In its pure form, it is highly explosive on contact with water. But most of the time, we encounter potassium in forms where it is much more stable.
In these non-explosive forms, potassium is an essential mineral for human life. Because it plays many important roles in your biology, you have to consume a small amount of potassium every day to remain healthy.
There are a couple reasons to suspect that potassium might be the active ingredient driving the weight loss we see on the potato diet. The first is that the potato diet provides stunningly high doses of potassium, amounts that most people would never otherwise consume.
For a long time, the recommended daily value for adults (technically, the “Adequate Intake”) was 4,700 mg of potassium per day. But most people don’t get anywhere near this amount.
In every CDC NHANES dataset from 1999 to 2018, median potassium intake hovers around 2,400 mg/day, and mean intake around 2,600 mg/day. In this report from 2004, the National Academy of Medicine found that “most American women … consume no more than half of the recommended amount of potassium, and men’s intake is only moderately higher.” Per this paper, only 0.3% of American women were getting the recommended amount. Similarly low levels of intake are also observed in Europe, Mexico, China, etc.
But in 2019, the National Academies of Sciences, Engineering, and Medicine changed the recommended / adequate intake to 2,600 mg/day for women and 3,400 mg/day for men. They say that the change is “due, in part, to the expansion of the DRI model in which consideration of chronic disease risk reduction was separate from consideration of adequacy,” but we can’t help but wonder if they changed it because it was embarrassing to have less than 5% of the population getting the recommended amount.
In any case, recommended potassium intake is something like 2,500 to 5,000 mg per day for adults, and many people don’t get enough.
Potatoes are exceptionally high in potassium. A single potato contains somewhere between 600 and 1000 mg of potassium, depending on which source you look at. They are the 6th highest in potassium on this list of high-potassium foods from the NIH, and 9th on this old list from the USDA. If you do the math, this means that someone on the potato diet, eating 2,000 kcal of potatoes a day, gets at least 11,000 mg of potassium per day, more than twice the old recommended intake.
Some people on the potato diet found their appetite decreased so much that they were only eating about 1,000 calories per day — but even then, they would still be getting around 5,500 mg of potassium.
Only 2.8% of Americans in the NHANES data got 5,500 mg per day or more. Only 0.06% were recorded as getting 11,000 mg/day or more. Clearly, the potato diet provides way more potassium than most people would ever get in their day-to-day lives.
One study, published in 2019, looks at the relationship between potassium intake and weight loss. As far as we know, it’s the only study of its kind (if you know of any others, send ‘em our way). In this study, sixty-eight people were enrolled in a “moderate low calorie/high protein Mediterranean diet” for a year. People generally lost weight, and “the strongest correlate of the decline in BMI was the increase in dietary potassium intake.”
In the aggregated publicly-available NHANES data from 1999 to 2018, potassium intake is negatively correlated with BMI (r = -0.055, p < .001) and log BMI (r = -0.051, p < .001). Because of complications around body size (taller people consume more food anyways, and therefore more potassium), we actually think that potassium per calorie, or potassium density, is the more appropriate measure. The relationship here is weaker (r = -0.031 with BMI, r = -0.022 if BMI is log-transformed), but still significant because of the large sample size.
But the really interesting thing is that the relationship gets stronger year-to-year across the span of the NHANES data. Here it is with both BMI and potassium density log-transformed. The relationship holds regardless of transformation, but log-transformation makes for the clearest visualization:
The relationship between potassium density and BMI is not significant in the early years of the NHANES data. From 1999 to 2010, the correlation is always consistent with zero, and p-values are always .20 or greater, even with these very large sample sizes. The sign of the nonsignificant relationship flips back and forth between positive and negative.
But in the 2011-2012 dataset, the relationship is negative, and the p-value drops below 0.10 for the first time. In the 2013-2014 dataset, the relationship is negative and significant (p < .001). In the remaining two datasets, 2015-2016 and 2017-2018, the correlation gets stronger and stronger. By 2017-2018, the correlation is r = -0.095. Aggregated across all years, the relationship is “only” r = -0.024, but that obscures the fact that the correlation has been increasing since around 2011.
There are certainly alternative explanations for this finding. For example, people who eat a diet that is higher in vegetables might both have lower BMIs and get more potassium on average. But it’s hard to come up with an explanation for why the relationship has been increasing, especially since potassium consumption / dietary potassium density haven’t changed at all over the same timespan:
This analysis doesn’t tell us much by itself. It isn’t strong evidence that potassium can cause weight loss, and doesn’t convince us of anything in particular. But it’s genuinely pretty weird, and since we don’t have much other correlational evidence, we thought it was good to mention.
The final reason to suspect that potassium might cause weight loss is that we tried taking small doses of potassium for a couple of weeks and we lost weight right away.
Two of the SMTM authors did a self-experiment where we took small doses of Nu-Salt and tracked our weight over time. Nu-Salt is just potassium chloride (KCl) in a salt shaker, marketed as a sodium-free alternative to table salt. You can buy Nu-Salt shakers online, at many local grocery stores, or even at Wal-Mart.
We started with two doses of 1/8 teaspoon Nu-Salt (about 330 mg potassium) twice a day and worked up from there. Straight potassium chloride is kind of gross (at least to us, your mileage may vary), so most of the time we mixed the KCl with a drink like Vitamin Water or Gatorade and just chugged it, though occasionally we mixed the potassium into food. Eventually we worked up to doses of 1/2 teaspoon a few (usually 2) times a day.
The first SMTM author to try this lost 5 lbs over the first 10 days, and then hovered around 5 lbs down for the remainder of the four weeks. At the lowest point, they were down 8.4 lbs.
The second author to try potassium supplementation lost 6 lbs over four weeks. They found this so easy that they kept going, and ended up losing a total of 12 lbs over 60 days. Some say they’re still taking potassium to this day (they are).
Here’s the graph for that second author. Note the two gaps when they weren’t able to weigh themselves because they had social commitments — a concert (the first gap) and a fishing tournament (the second gap).
This weight loss is modest, but surprising given that neither of these authors were very heavy to begin with. We also didn’t do anything else to try to lose weight — we weren’t sleeping more or eating better or doing more cardio. All we did was start taking some extra potassium. Honestly we are shocked. This is kind of unbelievable and we need other people to try it because we are so shocked.
Supplementing potassium, even at these low doses, felt a lot like being on the potato diet. From the start, we felt fidgety and sometimes hypomanic.
As on the potato diet, we noticed we needed more salt (i.e. more sodium) and more water, but we didn’t always crave salt or feel thirsty, and we had to consciously eat more sodium and drink more water to avoid feeling bad. A related side-effect is that salty foods like potato chips no longer taste salty — we suspect this is because the body needs so much sodium to balance out the potassium that it has “taken the brakes off” the mechanisms that normally make you stop cramming pickles into your mouth. Even straight table salt didn’t taste overwhelmingly salty.
We eventually figured out that you can put table salt into the same glass of water as potassium salt and drink them at the same time. This helps make sure you’re getting more sodium to balance out the potassium, and it also seems to make the potassium taste less weird.
We mostly did half as much sodium salt as potassium salt, a 1:2 ratio — for example, if we were taking a dose of 1/4 tsp potassium salt in water, we would add 1/8 tsp sodium salt to the same glass. But we’re not sure what the best ratio is, and we notice that some electrolyte powders have much higher ratios. For example, LMNT contains 1000 mg sodium for every 200 mg potassium. This seems like a lot but maybe a 5:1 ratio is better, people seem to like the taste of this stuff.
Like on the potato diet, we found our appetites diminished — what had been regular-sized meals made us feel stuffed like we had just finished Thanksgiving dinner. And just like on the potato diet, what little hunger remained was “weird” and easy to miss.
When we did feel hungry, it didn’t feel like a “problem”, and we sometimes went too long without eating and ended up feeling like crap. Hunger usually manifested as headaches, fatigue, and mood changes, rather than the physical signs we’re used to. Again, this sounds like the potato diet. For reference, this is how some people described the experience of hunger on the potato diet:
All this sounds a lot like the potato diet. But that in itself is kind of mysterious. People on the potato diet were getting about 10,000 mg of potassium a day. In comparison, we never supplemented more than 4,000 mg a day, and started the first day with only 660 mg. So it’s worth musing over why we lost weight on such small small doses.
One possibility is that small amounts of straight potassium salt act as a bolus dose. Potassium in food is essentially a slow-release formulation, but straight KCl in solution might be absorbed much more quickly and directly. This means that relatively small doses of potassium salts may lead to bigger spikes in blood potassium. If potassium causes weight loss by reaching a certain serum level, or by reaching the brain, a bolus may be much more effective than an extended-release formulation, which is what you would get in food.
We were also taking a different form of potassium than is found in food. The potassium compounds found in fruits and vegetables “include potassium phosphate, sulfate, citrate, and others, but not potassium chloride.” Not to mention the fact that we were dissolving the salt into drinks, so really we were getting straight potassium ions, not compounds that needed to be digested.
And in our case, we not only took our KCl in a drink, we tended to chug it all at once. It takes like 5-10 minutes to finish a plate of potatoes; compare that to chugging 330 mg K+ in a Vitamin Water in 10 seconds flat. Even if the potatoes contain more potassium, the pure ions hitting your stomach in such a small window might make a big difference. This might also contribute to a bolus effect.
We also tended to take our first dose early in the day, often before we had eaten our first meal. If potassium suppresses your appetite, you might get more of an effect if you take it before food. If you’re getting your potassium from food, you literally can’t take it before food.
A final explanation is that we were somehow primed for weight loss and weird side-effects from doing potato diet self-experiments. Both authors had been self-experimenting with potato diets before trying potassium supplementation, and it’s possible that after several months of high potato intake, pure potassium has more of an effect. We don’t know enough to say anything with confidence yet. But you know, that’s why we want to do a bigger study.
An important consideration when thinking about new theories is, if this were true, could we have missed it? For example, we can be pretty confident that cheese doesn’t cure cancer, because if it did, someone probably would have noticed by now (compare XKCD’s The Economic Argument). So in this case we should ask ourselves, if dietary potassium leads to weight loss, could that have really flown under the radar? What are the chances that (almost) everyone would have missed it?
We think it’s possible. The potato diet gives an exceptionally high dose of potassium, much higher than the recommended amount and more than almost anyone is getting in their normal everyday diet. If doses in this range reduce obesity, we probably wouldn’t have noticed because people almost never consume such large amounts on a daily basis.
While there seems to be a relationship with BMI in the normal dietary range, that relationship is hard to detect. The relationship in the NHANES data isn’t even statistically significant until 2013-2014, so people have had less than ten years to notice it. The correlation in the dietary range is also quite small, only about r = 0.05. You need a sample size of 783 observations to have just 80% power to detect a correlation of 0.10, and the correlation between BMI and potassium has never been that high, at least not in the NHANES data. If you want 90% power to detect a correlation of r = 0.05, you need 4,200 observations. So aside from in the NHANES, there haven’t been many chances to notice this either.
Even when people do supplement potassium, they tend to take really tiny amounts. Potassium supplements and multivitamins pretty much always contain 99 mg potassium or less. This appears to be the result of a ruling by the FDA, which says that oral potassium chloride supplements that provide more than 99 mg potassium are unsafe because they have been associated with small-bowel lesions. (This ruling only applies to non-prescription pills; prescription potassium tablets often contain more than 100 mg.)
We can’t quite tell if the FDA has regulated that you can’t put more than 99 mg in a supplement, or if they just require you to add a warning about small-bowel lesions and all the manufacturers have decided not to risk it. The relevant ruling appears to be 21 CFR 201.306, which does not seem to be a regulatory action, but there’s also something in the Federal Register from 1992 (57 FR 18157) which we haven’t been able to find. In any case, this appears to be the origin of the practice.
We are pretty sure that limiting potassium to 99 mg does not make sense and is wrong, for several reasons. First of all, we know that people can handle doses of potassium above 99 mg in some form or another, because people get several thousand mg from their diets every day. And potassium chloride is not the only way to consume potassium. Even if potassium chloride did somehow cause small-bowel lesions, people could take potassium citrate or potassium phosphate instead.
It’s not even clear what the original ruling was based on. This page from the NIH points to this document as a reference for the ruling, but that document just lists “all solid oral dosage form drug products containing potassium chloride that supply 100 milligrams of potassium per dosage unit” under the heading “216.24 Drug products withdrawn or removed from the market for reasons of safety or effectiveness”, and doesn’t give any reason why they were withdrawn.
The original ruling from 1975, 21 CFR 201.306, doesn’t cite any sources, and it is pretty noncommittal about the state of the evidence:
There have been several reports, published and unpublished, concerning nonspecific small-bowel lesions consisting of stenosis, with or without ulceration, associated with the administration of enteric-coated thiazides with potassium salts. These lesions may occur with enteric-coated potassium tablets alone or when they are used with nonenteric-coated thiazides, or certain other oral diuretics. … Based on a large survey of physicians and hospitals, both United States and foreign, the incidence of these lesions is low, and a causal relationship in man has not been definitely established. Available information tends to implicate enteric-coated potassium salts, although lesions of this type also occur spontaneously.
As far as we can tell, this was all prompted by a small number of articles from the 1960s. This article from 1965 reports six cases of “non-specific ulceration of the small intestine presenting as intestinal obstruction, perforation or haemorrhage” in patients taking “Hydrosaluric-K (enteric-coated hydrochlorothiazide with potassium chloride)”.
You’ll notice that both of these sources are saying something much more specific than just “potassium bad”. This article, also from 1965, makes it pretty clear that it thinks that enteric-coated potassium supplements, specifically, are to blame:
In 1957 the first of the group of thiazide diuretics was introduced. Because increased potassium excretion is one of the pharmacological effects of these thiazides, from the beginning of their use the supplementary administration of potassium has been a common procedure for protection against the potentially serious hazard of hypokalemia. In 1959, the first of several combinations of a thiazide diuretic with potassium chloride in a single tablet was introduced; some of these combinations are enteric coated while others are not.
Since 1957 there has been a striking increase in incidence of small-bowel ulcerative lesions. Recognition that these are related to the ingestion of enteric-coated potassium chloride is due primarily to the observations of Lindholmer et al in Sweden and Baker et al in this country.
Enteric coating refers to a polymer barrier applied to a pill or supplement that keeps it from dissolving in the stomach. Pills are coated this way for various reasons, but the end result is that the drug or substance is delivered to the intestines, rather than to the stomach. The second paper here is pretty confident that delivery to the intestine, rather than the potassium salt per se, is the problem. “A new preparation is necessary,” they say, “which will not … release potassium suddenly in the small intestine permitting absorption of a high concentration of the potassium chloride.”
Even with enteric coating, these lesions appear to be pretty rare. In that first set of six case studies, the authors note that, “in view of the widespread use of enteric-coated diuretic and potassium chloride tablets, constricting ulcers of the small intestine must be a very rare complication.” They cite only 53 cases from 1963 to 1965, “in which 48 patients had been taking enteric-coated thiazide and potassium chloride tablets, three patients may have been, and two had not.”
All the original sources seem to make it clear that enteric-coated potassium tablets are the thing to watch out for, not potassium itself. This was preserved in the 1975 ruling (“nonspecific small-bowel lesions … associated with the administration of enteric-coated thiazides with potassium salts”), but somewhere along the way the message was muddled and people got confused, and started thinking any potassium pills were potentially dangerous.
This appears to be a misconception. Though it’s not easy to find in a supplement, people regularly take prescription tablets of more than 100 mg potassium chloride and are just fine. Plain old potassium chloride seems pretty safe, and we can say that with some confidence because it’s something that has been the subject of many studies.
(Sadly none of these studies seem to have tracked body weight.)
In this hypertension study from 1985, participants were given about 2,500 mg potassium a day as “Slow-K (Ciba) eight tablets a day” for a month. They don’t report any negative events.
In this hypertension study from 2005, participants in one arm of the study were given about 3,700 mg potassium a day as “12 Slow-K tablets”. This lasted for a week and as far as we can tell, everyone was ok — they certainly don’t mention any bowel lesions in the paper. [Edit: We missed it the first time around, but this study did track body weight. People in the trial lost an average of 0.1 kg (0.22 lbs) over 7 days on potassium citrate, and an average of 0.3 kg (0.66 lbs) over 7 days on potassium chloride. They don’t seem to report a test against baseline but it probably would not be significant because the sample size was only 14.]
These Slow-K tablets themselves are just over 300 mg potassium in a “sugar-coated (not enteric-coated) tablet”. Taking 12 of them a day for a week seems to work out just fine.
In this chronic kidney disease study from 2022, participants were given a daily dose of about 1,500 mg potassium in “two capsules, three times per day during meals”. This presumably works out to a total of six capsules a day, or about 250 mg potassium per capsule. In this group with chronic kidney disease, 11% (mostly the older participants) did develop hyperkalemia. But no one developed small-bowel lesions.
We could keep going like this for a while — many studies give people several thousand milligrams of KCl per day, in forms that contain well over 100 mg of potassium per tablet. As long as tablets aren’t enteric-coated, and people don’t have chronic kidney disease, this turns out just fine. KCl by itself at reasonable doses is quite safe. You can literally buy sacks or jugs of potassium chloride on Amazon, mostly for use in electrolyte solutions (i.e. make your own Gatorade).
The design of the study is simple: supplement low doses of potassium directly, and see if people lose weight. Super easy, low cost. And you’re probably not getting enough potassium to begin with.
This design is similar to the design we used for the potato diet. The main difference is that you will be chugging potassium salt solution instead of eating potatoes, and you can keep eating normal food like usual.
This study will run the same length as the potato diet so that the two can be compared directly — 28 days, with the final weight measurement on the morning of day 29. But we encourage people who are having a good time with the potassium to keep going and report back again at 60 days.
We recommend that you use Nu-Salt as the source of your potassium chloride, because that is what we tried and it worked for us. All terms and measurements below will be in Nu-Salt terms; if you use something else, make sure to convert all units to whatever form of potassium you are eating.
You can buy 3 oz shakers of Nu-Salt in various places, including on Amazon. A 3-pak should be enough to cover 28 days of potassium supplementation for most people, but if you want to share with your friends and family, or you’re confident you want to supplement potassium for longer, you can also buy a 12-pak.
There are many other potassium chloride brands you could try if you want, like this Morton salt substitute (though we tried this one and found it to be *extra* gross). You could also try another potassium compound, like potassium citrate. We would prefer that most of you stick to KCl, but if a few of you tried other compounds that might be interesting, in case they end up being clearly much more or much less effective.
We’re asking participants to buy their own potassium, and we feel ok about this because potassium salt is pretty cheap, only about 80 cents per ounce. As of this writing, the 3-pak of Nu-Salt Shakers (totaling 9 oz of KCl) is only $7.48 on Amazon. But if you want to participate in this study and you really can’t afford it, contact us and we’ll send you some.
How to Consume
Potassium chloride by itself tastes pretty gross to most people, bitter and metallic all at the same time. This gang of Australian teens tasted all the alkali metal salts, and if you can get past their literally nauseating camerawork, you’ll see that they describe potassium chloride as “really bad” and “weird” and “cold on my tongue” and “it tastes like how bleach smells” and “oh god, what is it?” They still gave it a 3/10 though, which is a higher rating than they gave cesium chloride.
The good news is that it doesn’t take much to mask this unpleasant taste. If you mix the potassium salt into food or beverage, it becomes much easier to handle.
We fooled around with a few approaches, but ultimately we found that it’s easiest to just dissolve the KCl in a glass of water, or Gatorade / Powerade / Vitamin Water. Often we did potassium in a mixture of half water and half one of these drinks. The flavor of 1/8 tsp KCl in a 20 oz drink is pretty understated — the water just feels “smoother”, almost like a fancy mineral water. Which it kind of is.
You can improve the taste a little more if you also add a bit of table salt (NaCl). We found that a mix of 2:1 KCl to NaCl tastes pretty ok — not too salty and not too metallic. For example, if you were putting 1/4 tsp KCl in a Gatorade, adding 1/8 tsp NaCl is a good idea to keep the potassium taste from being overwhelming. But some electrolyte powders contain higher ratios and may be more effective/taste better, so feel free to experiment with adding more (or less) NaCl.
Adding lemon juice or sugar can also help offset the taste. As you can imagine, if you take this line of thinking to its natural conclusion you’ll end up drinking slightly salty lemonade. It’s not too bad.
We also sometimes tried putting the KCl in food. You can hide small doses in flavorful foods like beans, or in sauces, but if you overshoot at all, the food ends up tasting pretty weird.
Our most successful food discovery is that KCl goes really well with mustard. You can mix 1/4 teaspoon into a generous helping of mustard and barely taste it at all. If anything, KCl gives the mustard a tingly, almost effervescent feel.
If we were normal influencers, this is where we would start promoting DR MOLD-TIME’s KALIATED WEIGHT LOSS MUSTARD. Sadly we don’t know how to sell condiments, but hit us up if you want to do a partnership.
How to Supplement:
Take at least one dose per day.
But no more than 4 doses per day.
Always take doses at least an hour apart.
Take doses with plenty of water. It’s also recommended you take them with some table salt, or eat something salty right after.
We recommend that each dose be at least 330 mg potassium (1/8 tsp Nu-Salt).
However, never take more than 1300 mg potassium (1/2 tsp Nu-Salt) in a single dose.
This means the maximum daily dose from KCl supplementation is 5200 mg, which is high but still less than you would get on the potato diet.
If you have to miss a few days that’s fine, just pick it back up when you can.
In the grand scheme of things, these are pretty low doses. A few hundred milligrams of potassium isn’t much, and this dosing scheme will never give you anywhere near the amounts of potassium people were getting on the potato diet.
If this setup doesn’t cause weight loss, it’s still possible that potassium could be the active ingredient in the potato diet, and the dose on this protocol is simply too low to budge your lipostat. But, safety first, and we hold out hope that small doses may have clear effects, even if the effect of this study is smaller than the potato diet.
Now that we’ve established these basics, here’s the study protocol:
Start with two doses of 330 mg potassium (1/8 tsp Nu-Salt) on the first day.
If you feel fine, try three or four doses of 330 mg potassium (1/8 tsp Nu-Salt) on subsequent days.
If you’re feeling fine after 4-7 days, try one dose of 660 mg potassium (1/4 tsp Nu-Salt).
If you still feel good, keep increasing your dose by small increments. For example, if you are on two doses of 660 mg (1/4 tsp Nu-Salt) a day, you might increase that to three doses of 660 mg, or one dose of 660 mg and one dose of 1300 mg (1/2 tsp Nu-Salt). If a higher dose makes you feel bad, try returning to the dose you were on before and maintain that.
Try slowly increasing to two doses of 1300 mg (1/2 tsp Nu-Salt) a day. Only go beyond that if you are feeling totally fine.
You should calibrate based on your own experience — different people will have different needs and different limits. For example, we’d expect someone who weighs 300 pounds would be able to tolerate higher doses than someone who weighs 150 pounds.
If you feel weird / bad / tired / brainfog and you can’t tell why, try:
drinking some water;
getting some sodium;
and see if any of those help. It may be easy to end up needing food / water / salt and not notice.
If you still feel weird, try dropping to a lower dose or taking 1-2 days off.
If at any point you feel sick or have symptoms of hyperkalemia (see below), stop immediately and seek medical attention.
This is not a diet. You should continue eating as normal, and food should mostly be consumed ad libitum (eat as much as you want). But there’s one important guideline we want to note. Because potassium supplementation seems like it strongly reduces appetite in some people, you may actually need to eat more than you feel like. We strongly encourage you to make sure you get at least 1000 calories a day, preferably more.
It’s fine to take breaks in the middle or even stop the trial early. But if you sign up, please record 4 weeks of data even if you stop taking potassium at some point, have to end early, have to take a break in the middle, or can’t stand taking KCl for the full 4 weeks. If you do it for two days and hate it, please keep recording your weight and potassium consumption (which would just be zero from then on) for the full 29 days and submit your data as normal. We can still use it!
Our hope is that this will keep us from running into the dropout issues we had in the potato diet. Anyone who records data for 29 days is clearly taking the study seriously, even if they weren’t able to stick to the potassium supplements the whole time.
Based on this, our main analysis will focus on participants who provide 4 weeks of data. If you provide a weight measurement for the morning of day 1 and the morning of day 29, so we can calculate your weight before and after, and you took at least one dose of potassium, we will do our best to include you in the analysis.
Speaking of which, here are the variables we want you to track.
The main outcome of interest is your weight, taken every morning, after your first “void”, assuming you void in the morning.
We also want you to track your potassium supplementation. We’ve provided four fields per day for potassium doses and notes, since we ask that you take no more than four doses per day.
There’s a possibility that potassium causes weight loss by protecting you from lithium, and there’s a chance that certain foods are especially high in lithium. We aren’t confident enough about this to ask you to avoid these foods, but we do want to ask you to track how much you’re eating them. We’ve provided fields for meat, eggs, dairy, leafy greens, and tomato products, all of which are currently top lithium candidates. If you eat more than a smidge (by your own judgment) of any of these foods, please put a “1” in that field for that day. If not, put a “0”.
This way, we can see if any of these foods seem to inhibit potassium weight loss. Relatedly, if you’re supplementing potassium and not seeing any weight loss, you could always try cutting back on the cream and ketchup.
We’ve also included fields for several BONUS VARIABLES. You don’t have to track these, but if you do, the standardized fields will let us analyze these results across participants. In particular, we’d be interested in having data for your blood pressure, sodium intake, and energy/mood, but we’ve included several more fields for variables people might want to track. There’s also a field for tracking waist circumference, which a couple people asked for after the potato diet.
We also included fields for up to 10 extra variables of your choosing. If you want to record anything else, please put it here. This way you can add more variables without changing the format of the data sheet, which would make it harder to analyze your data. So please don’t touch the formatting, but feel free to add variables in the extra variables area.
And speaking of other variables — Michael Dubrovsky of SiPhox reached out to us to offer a discount to participants who want to test their blood biomarkers with SiPhox’s at-home Quantify kits. We haven’t had a chance to try these kits, but if you’re interested check it out. You can get a two-kit bundle (so you can do one test before the trial and one after) for 40% off at this link.
That’s the gist. Before you sign up, however, we insist you read this section on safety:
Do not participate if you have diabetes or any kind of impaired kidney function.
For everyone else, this level of potassium supplementation should be very safe.
Until recently, it was recommended that adults get 4,700 mg of potassium per day in their diet. Most people seem to get less than this, so supplementing is probably a good idea anyways.
Going over 4,700 mg of potassium a day is also very safe. Most people in the NHANES data got less than the recommended amount, but a small number were estimated to get over 10,000 mg in their diet. The potato diet also seems to indicate that you can take a lot of potassium and not get sick. As a reminder, 2000 calories of potatoes gives you more than 10,000 mg of potassium.
In addition to recommended allowances, the National Academy of Medicine also sets tolerable upper intake levels (ULs) for vitamins and minerals. But normal doses of dietary potassium are so safe that no upper level has been set, for lack of information. This chapter from the National Academy says, “Although dietary potassium intake can be increased through behavioral change, there is a self-limiting aspect to such changes that makes toxic adverse effects from increases in dietary potassium intake unlikely.”
This study focuses on potassium chloride specifically, which is quite safe. It’s sold as a salt substitute and electrolyte powder — you can buy it in bulk on Amazon. Studies of hypertension sometimes prescribe as much as 3,700 mg potassium a day as potassium chloride, without any apparent ill effects.
The toxicity of potassium chloride is low. The LD50 for potassium chloride taken orally is around 2,500 mg per kilogram of bodyweight. If you weigh 165 lbs, you would start to be in danger at doses of around 190,000 mg.
Like any substance, very large doses can be dangerous. The main danger is unsurprising — hyperkalemia, which is the condition of having too much potassium in your blood. But to get there, you have to A) take a lot of potassium, B) have kidney problems, or C) both.
The National Academy summarizes the few case studies that are known. The first is from 1978, a 32-year-old woman who died after ingesting an estimated 47 extended-release potassium chloride tablets.
The second is from 2014, a report of a 26-year-old man who died after consuming an estimated 12,500 mg of potassium, in the form of extended-release potassium chloride tablets. However, “there was also co-ingestion of dextropropoxyphene-acetaminophen in this case, which complicates the interpretation.”
These are the only deaths they report (“death is a particularly severe endpoint to use to establish a UL”), but they review two other case studies as well. One is a case report of a 17-year-old man who developed nausea, vomiting, and diarrhea after consuming around 10,000 mg of potassium as sustained-release potassium chloride tablets.
Another describes a 67-year-old man with kidney injury who had a heart attack after consuming around 2,730 mg per day of potassium from a salt substitute for one week. He also “reportedly consumed a high-potassium diet, in addition to the salt substitute.” They note that, “the amount reportedly consumed from the salt substitute is a level of intake that has been repeatedly studied in potassium supplement trials, wherein the risk of adverse events appears to be low among generally healthy populations.” We agree — 2,730 mg per day seems very safe if you are not a 67-year-old man with a kidney injury.
The worst-case scenario in this study is that you develop hyperkalemia. If you have healthy kidneys, this shouldn’t happen. But just in case, here are the signs and symptoms.
Symptoms of mild hyperkalemia include muscle weakness, numbness, tingling, and nausea. These could also indicate that you’re not getting enough food, water, or sodium. If you start feeling these symptoms, try eating, drinking some water, or having some table salt or salty food. If the symptoms persist or get worse, consider ending the study or at least taking a break.
Symptoms of severe hyperkalemia include abnormal heart rhythm, heart palpitations, shortness of breath, chest pain, sudden nausea, and vomiting. If you have any of these symptoms, end the study immediately and seek medical attention. If you have an existing reason you might experience one of these symptoms (you already sometimes have heart palpitations or get nauseous suddenly), do not sign up for this study, since if you had symptoms of hyperkalemia, you wouldn’t be able to tell.
Ok, now you can sign up.
The only prerequisites for signing up are:
You must be 18 or older;
In generally good health and specifically with no kidney problems;
Willing to supplement potassium, as described above, for at least four weeks, and;
Willing to share your data with us.
Also, we’d prefer that you don’t sign up for this study if you were already a participant in the potato diet study. We’d love to have your help again, it’s just that if you lose even more weight on potassium, that will mess up the 6-month weight-loss followup numbers for the potato diet. Those of you who have tried the potato diet but weren’t officially part of our study can still sign up.
As usual, you can sign up to lose weight, lower your blood pressure, get more energy, or see one of the other potential effects. But you can also sign up to help advance the state of nutritional science. This study will tell us something about nutrition, by either supporting the idea that potassium is the reason the potato diet causes weight loss, or providing evidence against it.
Beyond that, running a study like this through volunteers on the internet is a small step towards making science faster, smarter, and more democratic. As always, that seems like a future worth dreaming of, and if you sign up, you get us closer to that future.
Potassium salt is a little gross, so you might be wondering if you really want to commit to this for several weeks. But here’s our suggestion: If you are at all interested in trying it, go ahead and sign up and start collecting your data. Try the first day or two and see how it feels. If you hate it and have to stop, we would still love to have that data.
If you want to go for longer than four weeks, that’s great, we would be happy to have more data. Report your data at four weeks like normal and then just keep going, and if you make it to 60 days, send us an update.
If at any point you get sick or begin having side-effects, stop the diet immediately. We can still use your data up to that point, and we don’t want anything to happen to you.
We are mostly interested in weight loss effects for people who are overweight (BMI 25+) or obese (BMI 30+), but if you are “normal weight” (BMI 20-25) you can also sign up. The potato diet caused weight loss in people of normal weight, and it would be interesting to see if the same thing happens here.
And for everyone, please consult with your doctor before trying this or any other weight loss regimen.
Anyways, to sign up:
Fill out this google form, where you give us your basic demographics and contact info. You will assign yourself a subject number, which will keep your data anonymous in the future.[UPDATE: Signups are now closed, but we plan to do more studies in the future. If you’re interested in participating in a future study, you can give us your email at this link and we’ll let you know when we run the next study.]
We will clone a version of this google sheet and share the clone with you. This will be your personal spreadsheet for recording your data over the course of the diet.
On the first day, weigh yourself in the morning. If you’re a “morning pooper”, measure yourself “after your first void”; if not, don’t worry about it. We don’t care if you wear pajamas or what, just keep it consistent. Note down your weight and the other measures (mood, energy, etc.) on the google sheet. Start with two doses of 330 mg potassium (1/8 tsp Nu-Salt) on the first day. On day 2, weigh yourself in the morning, note down data in the sheet, then take at least two doses of 330 mg potassium (1/8 tsp Nu-Salt). On day 3, etc. See the dosing protocol above for details.
We prefer that you keep taking at least one dose of potassium a day for at least four weeks. But if you do have to miss some days, or need to take a break, just note that down and keep recording other variables. If you totally can’t stand the potassium, just stop taking it, keep recording other variables until day 29, and submit your data as normal, we can still use it.
When you reach four weeks, and take your weight measurement on the morning of day 29, send us an email with the subject line “[SUBJECT ID] Potassium Trial Complete”. This will let us know to go grab your data. This is also your opportunity to tell us all about how the study went for you. Please tell us any data that doesn’t easily fit into the spreadsheet — how you felt, what kind of potassium you used, before and after pictures (if you want), advice to other people trying this, etc.
You may reach day 29 and decide to keep going longer. That’s fine. Send us an email on day 29, and if you reach 60 days, send us another email and we will grab your data again. If we get enough data we might do an analysis of this longer span as well. If you go past 60 days and want to share it with us at some point, that’s cool too.
If we have our act together, we will send each of you a brief google form following up at future points.
Assuming we get 20 or so people, we will write up our results and publish them on the blog. We would really like to get a couple hundred people, though, since at that point it becomes possible to do more complex statistical analyses. So if you think this is an interesting idea, please tell your friends!
Special thanks to Austin Vernon for helping us automate parts of the signup process.
Lithium is an element, atomic number 3. It is a soft, light, highly reactive metal with a variety of uses. Among other things, it’s often found as a trace mineral in drinking water. Small amounts of lithium are naturally present in many water sources, but levels of lithium in American drinking water have been increasing for the past 60 years.
In 2021, the USGS released a report that found a median level in US groundwater of 6.9 µg/L. This is almost four times the median level in the 1960s, but looking at nothing but the average obscures the fact that many people are getting exposed to even more. For comparison, the maximum level they found in groundwater was 1700 µg/L, ten times the maximum recorded in 1964.
The USGS also found that about 45% of public-supply wells and about 37% of domestic-supply wells contain concentrations of lithium “that could present a potential human-health risk per the current EPA guidelines”. Here’s how they describe it in the paper:
Lithium concentrations in untreated groundwater from 1464 public-supply wells and 1676 domestic-supply wells distributed across 33 principal aquifers in the United States were evaluated for spatial variations and possible explanatory factors. Concentrations nationwide ranged from <1 to 396 μg/L (median of 8.1) for public supply wells and <1 to 1700 μg/L (median of 6 μg/L) for domestic supply wells. For context, lithium concentrations were compared to a Health Based Screening Level (HBSL, 10 μg/L) and a drinking-water only threshold (60 μg/L). These thresholds were exceeded in 45% and 9% of samples from public-supply wells and in 37% and 6% from domestic-supply wells, respectively.
Lithium is not currently regulated in drinking water, and water quality reports don’t regularly include it. Most water treatment plants do not track lithium or attempt to reduce it. But the EPA and other government agencies are becoming more concerned about lithium exposure, even at the trace levels found in drinking water:
Just this January, lithium was added to the EPA’s proposed Unregulated Contaminant Monitoring Rule. The Rule is used by the EPA to collect data for contaminants that are suspected to be present in drinking water and that do not have health-based standards set under the Safe Drinking Water Act.
Although useful for treating mental health disorders, pharmaceutical use of lithium at all therapeutic dosages can cause adverse health effects—primarily impaired thyroid and kidney function. Presently lithium is not regulated in drinking water in the U.S. The USGS, in collaboration with the EPA, calculated a nonregulatory Health-Based Screening Level (HBSL) for drinking water of 10 micrograms per liter (µg/L) or parts per billion to provide context for evaluating lithium concentrations in groundwater. A second “drinking-water-only” lithium benchmark of 60 µg/L can be used when it is assumed that the only source of lithium exposure is from drinking water (other sources of lithium include eggs, dairy products, and beverages such as soft drinks and beer); this higher benchmark was exceeded in 9% of samples from public-supply wells and in 6% of samples from domestic-supply wells.
But these effects may not always require psychiatric doses. A long-running literature of epidemiological research (meta-analysis, meta-analysis, meta-analysis) suggests that long-term exposure to trace levels of lithium commonly found in drinking water can also have psychiatric effects. Specifically, trace levels in drinking water are often found to be associated with decreased crime, reduced suicide rates, and/or decreased mental hospital admissions.
So people often ask us, how can I get lithium out of my tap water?
For a long time, we weren’t able to answer this question. Until very recently, no one was concerned about lithium levels in drinking water, so there isn’t much research on how to get it out. Heck, back in 2014 the NYT ran an opinion piece arguing that maybe we should start putting lithium in our drinking water. How times have changed.
This is further complicated by the fact that lithium is pretty weird. At an atomic number of only 3, it is the third-lightest and third-smallest element. In some ways it is more like the gasses hydrogen and helium than it is like the metals iron, lead, or mercury, which are much larger and much heavier. This makes it hard to predict whether techniques that can remove other metals would also remove lithium, which is present in solution as an especially tiny ion.
(A favorite “Whoaahhh” fact about Li+ is that it is so small, a bit of electrical energy can make it can creep into the crystal lattices of other compounds and basically just hang out there indefinitely, usually with a bit of swelling of the “host” crystal. It’s kind of like pouring sand into a jar of marbles — lithium is so tiny it can sneak into very small spaces, which is virtually impossible with any other metal ion. The technical term is that it “intercalates” into these materials. Lithium intercalating back and forth between cobalt oxide and graphite, for instance, is the basis of the lithium ion batteries that power virtually every phone and laptop and electric vehicle. There’s an entire field of research focused on making lithium creep into and out of various materials to store energy. People have been trying for a long time to make Na+ do this, since Na+ is so much cheaper and more abundant than Li+, but it’s still way too hard to make any kind of useful battery with an ion as big as Na+.)
To answer the question of how to get lithium out of your drinking water, we set up a project with research nonprofit Whylome to test several commercially-available water filters, the kinds of things you might actually buy for your home, and see how good they are at removing lithium. It’s taken a couple of months of planning, testing, and analysis, but those results are finally ready to share with the world.
This project was funded by generous donations to Whylome from individuals who have asked to remain anonymous. Further support for the research was provided by The Tiny Foundation, which allowed us to expedite several aspects of the research. Special thanks to our funders, Sarah C. Jantzi at the Plasma Chemistry Laboratory at the Center for Applied Isotope Studies UGA for analytical support, and to Whylome for providing general support.
The full report is here, the raw data are here, and the analysis script is here. Those documents give all the technical details. For a more narrative look, read on.
You buy a bunch of normal water filtration devices (henceforth “filters”, even though they’re technically not all filters) from a store, like Home Depot, or online, from places like Amazon. Or online from Home Depot.
You spike large quantities of water with specific amounts of lithium, to get water containing known levels of lithium.
Then, you run the lithium-spiked water through the filters and take samples of the water that comes out the other end.
Finally, you submit that water to chemical analysis and find out how much lithium was removed by each of the filters.
This is basically the perfect garage experiment — except that in this case, filters were tested in the laundry room, not in a garage.
1.1 Water Filtration Devices
To get a sense of the different options available on the market, we elected to test three different types of devices: carbon filters (which are what most people think of when they think of at-home filters); reverse osmosis devices; and electric water distillation stills.
We chose devices from brands that most people have heard of, and models that people tend to buy. If you click through the links below, you’ll see that many of these devices are best-sellers.
Devices were purchased off of Amazon, from the Home Depot, or from their manufacturer, depending on availability. For each device, we also purchased as many extra filters as needed, so that each test could start with clean filters (see the report for more detail).
Carbon Filters — We came into this pretty confident that carbon filters would perform very poorly for lithium removal, despite some nonsense to the contrary floating around the internet (for example, here and here). Carbon has a low affinity for Li+, so we didn’t expect it would pull very much out of the water. Carbon can remove some metals, like lead, by ion exchange — the same principle used in water softeners. But the metals it is good at removing are multivalent (having a charge of +2 or +3 or +4), not +1 like Li+.
Carbon is also known for having noticeable variation between individual filters, because the carbon in question is made from plant material (often coconut). There will be minor variations in the carbon properties between batches, depending on how fast the coconuts were growing that month and minutiae like that. So we went into this expecting that there might be some differences between different filters, even within the same brand and/or model.
Since we expected that carbon filters would probably all suck based on the mechanism of action, and because we expected that there might be noticeable variation, we decided to test several different brands of carbon filters, in multiple configurations (pitcher, on-tap, and under-sink). This is why we tested so many devices and why we got a relatively wide mix of brands and configurations.
This way, if carbon filters are all equally ineffective, it should be very obvious. But if we’re wrong and they’re great, or some are much better than others, we have a good chance of noticing. Carbon filters are also the cheapest and most commonly used filters, another reason to test more of them.
We expected less variation in the other two kinds of devices, so we decided to test two models of each.
Distillation — We expected that distillation machines would work well, but we didn’t know if that was 80% well, 90% well, or 99.9% well. Lithium salts have zero volatility, so when water evaporates and condenses, the lithium should be left behind. The main risk is that droplets of liquid could get caught in the condenser, which could result in some of the original liquid getting into the clean distillate. So a well-designed distillation machine should perform well, but we didn’t know how reliable or well-designed small at-home countertop models would be.
Reverse Osmosis — We were the most uncertain about reverse osmosis. Reverse osmosis is very good at removing divalent metal ions (like Ca2+ and Mg2+), and pretty effective at removing monovalent metal ions from tap water (like Na+ and K+), but it wasn’t clear if this pattern would extend to lithium. In some ways Na and K are very similar to lithium — all three are present in water as single-charge positive ions, and all three are the same chemical group, the alkali metals. But lithium is much smaller and lighter than other elements. Na has an atomic number of 11, and K has an atomic number of 19, while Li has an atomic number of only 3.
As a result, we weren’t sure if reverse osmosis would be anywhere near as effective at removing lithium as it is at removing these other contaminants. Maybe reverse osmosis would pull lithium out of the water just like any other ion. Maybe it would miss lithium entirely, because the ion is so small. Or maybe something in between. So we went into this expecting that reverse osmosis might be anywhere from 0% to 100% effective.
1.2 Lithium Spiked Water
For realism, we worked with actual American tap water. In this case, we used tap water from the town of Golden, Colorado. Despite the fact that it was indeed part of the Colorado Gold Rush, Golden, CO is not named after the gold rush or even after gold itself; it is named after some guy named Tom Golden.
Samples of the tap water were spiked with known quantities of “ultra dry” lithium chloride salt to create spiked water samples of known lithium concentration.
We ended up testing four concentrations of lithium: 40, 110, 170, and 1500 µg/L Li+. This covers a range from “starts to be concerning” to “around the highest levels reported in US drinking water”. There’s also a bit more history to these numbers, but we’ll talk about that below.
Each filter was tested at each concentration, and at two timepoints (realistically these are “volumepoints”, but that’s not really a word). The carbon filters and the RO devices were each tested after 10 liters and after 20 liters. The distillation machines were tested at 2 liters and again at 4 liters, since they take a really long time to run.
Analysis was performed by ICP-OES. The instrument used was a Perkin Elmer 8300 ICP-OES, and the limit of detection was 1 µg/L. All analyses were done in triplicate and were submitted in a random order.
The following figure gives an overview of the results. This figure only includes performance at a concentration of 110 µg/L after the first timepoint (2L for distillation, 10L for the others) but the same general pattern holds across pretty much everything:
2.1 Carbon Filters
Carbon filters are lousy at removing lithium, but probably not 0% effective. Most of the time, water contained slightly less lithium coming out of the filter than it did going in. But the carbon filters didn’t do much, and there wasn’t a huge amount of variation between them.
2.2 Reverse Osmosis
Reverse osmosis was shockingly good at removing lithium. Removal was reliably high for all systems, more than 80% for the GE system and consistently above 95% for the APEC system. The result is unequivocal: reverse osmosis works. Reverse osmosis does not, however, drive these concentrations close to zero. RO is good, but if you start with 100 µg/L in your tap water, you might still end up drinking 10 µg/L even after filtration.
In many cases you do end up with less than 10 µg/L after filtration, but if you start with a high concentration, you are still generally getting more lithium than was in the median American water source in 1964 (2 µg/L). The lower your starting lithium, the lower the lithium concentration you are getting out of your RO filter.
Finally, distillation machines are nearly perfect at removing lithium. Lithium levels after distillation were undetectable (<1 µg/L) in most cases, and removal was still >99.5% for the highest concentration (1500 µg/L). Distillation reliably drives any levels you would expect to see in American tap water below the level of detection.
2.4 Long-Term Reverse Osmosis Test
We also decided to do one long-term test of a single system, to check if it kept performing well over a longer period of time, and to see if anything weird happened. We expected that systems would get slightly worse over time, but there might also be a discontinuity, where a system keeps doing well for a while and then suddenly craps out and does much worse. We wanted to see how much decline happened with more use, and check if there was any discontinuity or sudden point of failure.
Carbon filters don’t work very well even straight out of the box, so obviously we didn’t test one of those. RO doesn’t remove lithium from water quite as well as distillation, but it’s faster, cheaper, and much easier to install. Because RO sits at this sweet spot, we decided to test the GE RO device up to 100 liters.
We tested the GE RO device against a concentration of 170 µg/L, and the device continued to do a good job removing lithium even up to 100 L. Performance went down slightly over time, but not enormously. At 10 L, the device removed about 98% of the lithium in the water, and by 100 L, it removed about 89%. We don’t know how well it would perform beyond 100 L, but this finding suggests it would keep doing pretty well but progressively worse over time.
This would be a good topic for further study — run a few RO devices to 1000 L and see what happens. Alternately, you could install a RO device in the home of someone whose tap water is already high in lithium, test its effectiveness once a month, and get a sense of how these devices would perform in a real-world scenario.
The conclusions from this study are, fortunately, pretty straightforward. But on the way to those conclusions, there were a few complications.
3.1 PUR Pitcher
In addition to the six carbon filters mentioned above, we also tested the “PUR Ultimate Filtration 7-Cup Pitcher”. When we ran it through the same procedure as the other filters, we found there was more lithium in the filtered water than in the original water, at all concentrations. Basically it seemed like the PUR pitcher was adding lithium to the water instead of taking it away.
This was confusing and seemed like it might be wrong, so we tried the same pitcher again with a different set of filters. This time we didn’t get the weird result — lithium levels went down when we ran water through the filter, just like normal.
We’re not totally sure why this happened. One possibility is that some of the water evaporated during testing, but letting the water sit for a few days didn’t make a substantial difference compared to filtering rapidly, so this appears unlikely. Another possibility is that there’s meaningful batch-to-batch variation in the lithium content of the filter cartridges. Activated carbon comes from plants (usually coconuts), so conceivably there could be more lithium in some coconuts than in others. If you got unlucky, the carbon might contain a lot of lithium and you would end up adding lithium to the water instead of taking it away.
In any case, this was strange and inconclusive enough that we ended up removing it from the main analysis, but we’re reporting it here just in case. Good cautionary tale about how even a simple measurement is never simple.
3.2 Concentration Complication
We originally planned to test lithium concentrations of 10, 60, 100, and 1000 µg/L.
The reasoning was that 10 and 60 µg/L were the EPA thresholds of interest, and that testing 100 and 1000 µg/L covered two further orders of magnitude while still being realistic — according to the USGS, 4% of groundwater wells in the US contain more than 100 µg/L lithium, and the maximum recorded contained 1700 µg/L.
But two things happened to screw that up.
First, the tap water in Goldengave us a bit of a surprise. Golden is a city in Colorado, and most tap water in Colorado comes from dazzlingly clean snowmelt. Snowmelt should contain almost no lithium (it’s basically been distilled), so we expected that the tap water in Golden would also contain almost no lithium. This assumption was backed up by water quality reports from nearby Denver, CO, which find no lithium in Denver’s water.
But to our surprise, when we started testing samples, we found that they contained more lithium than we spiked them with. We circled back and tested the unspiked tap water, and found that it contained around 20-25 µg/L, an amount that was reliable across several months. If there are seasonal changes, our January-March sampling window wasn’t big enough to detect them.
The local water treatment plant is fed by Clear Creek, so we collected and tested a sample from the creek about 2 miles upstream from the water treatment plant. The creek there has a concentration of 27 µg/L, very similar to the tap water. It appears that water enters the Golden, CO treatment plant at around 25 µg/L, and the treatment process has very little impact on lithium concentration.
At this point we were questioning our assumptions about water sources, so we collected some local snow and tested that too. The snowmelt had barely detectable lithium, less than or equal to 1 µg/L. This confirms our earlier belief that precipitation is generally very low in lithium (at least in Golden, CO).
If it’s not in the snowmelt, the lithium must be coming from somewhere else. This is speculation, but the Clear Creek watershed does include many abandoned mines, some dating way back to the early gold and silver rushes from the 1800s, and there is at least one Superfund site, so old mine tailings are one possibility (see in particular here). One of the towns upstream (Idaho Springs) has natural hot springs with some geothermal activity, so another possibility is that these springs add lithium to Clear Creek along the way. We didn’t find an obvious link for Idaho Springs, but other hot springs in Colorado definitely brag about the lithium content of their water (Denver Post on Orvis Hot Springs: “The resort’s seven pools are laden with lithium…”), so this seems quite plausible.
This suggests that our original assumptions were mostly correct — snowmelt contains little to no lithium, so most drinking water in Colorado should be quite pure. But in this specific case, looking at water drawn from Clear Creek, we ended up with more than we expected. Water coming from one of Colorado’s snowmelt reservoirs, rather from a well or stream, would probably contain a lot less.
In the end, the lithium levels in Golden’s tap water raised the lithium level of all of our samples by about 25 µg/L. We were already halfway through testing when we discovered this, so we decided to continue with these slightly higher concentrations. If anything, it’s a stricter test of the filters.
Second, the lithium salt we used was substantially more potent than the stated strength (i.e. much stronger than expected), which also increased the concentrations we tested.
We used lithium chloride from Fisher Scientific as the lithium spike for all our samples. According to the certificate of analysis, the salt contained a lot of water. But apparently this was not the case. As far as we can tell, the salt appears to have very little water content, so it contains a lot more lithium per weight than expected (about 30% stronger than expected). This caused us to underestimate the amount of lithium in the salt, and as a result, we added more than we meant to. This is why we ended up testing up to 1500 µg/L.
Again, we were already halfway through testing when we discovered this, and decided to forge ahead. Because this error was propagated across all the samples we had submitted, the analysis was still internally consistent. Even though these weren’t the numbers we had set out to study, it doesn’t really matter. Those numbers were arbitrary to begin with; we chose them because we live in a base-10 world. We were still able to compare between filters at realistic concentrations.
Together, these two factors inflated the concentrations we tested, from 10, 60, 100, and 1000 µg/L to 40, 110, 170, and 1500 µg/L. First, the tap water from Golden added 25 µg/L to all the samples. Then, the unusually dry lithium salt inflated the amount added to each sample by around 30%.
Fortunately, this does not seriously impact our results. Filters were consistent across all concentrations, and in the end we covered a very similar range, 60-1500 µg/L instead of 10-1000 µg/L. We’re only really missing an analysis of how well the filters would work at low levels, around 10 µg/L. But RO devices that drive 40 µg/L to around 1 µg/L can also be expected to drive 10 µg/L way down low.
The only thing we would want to revisit in future studies is to test carbon filters at levels close to 10 µg/L; but our best bet is that they don’t do much at those levels either.
We also caught one other problem. During analysis, we found that we made a mistake when mixing four of the concentrations. Twice as much lithium chloride as intended was added to the solutions for the PUR faucet mount at concentrations of 110 and 170 µg/L, and also for the Culligan faucet mount at 110 and 170 µg/L. As a result, these two filters were actually tested against ~210 µg/L and ~325 µg/L instead of the intended 110 and 170 µg/L. You can easily see this error if you look at the tables in the report.
This is unfortunate and does complicate the data, but again it doesn’t seriously change the conclusions. Carbon filters don’t get much lithium out of tap water at any concentration, whether it’s 110, 170, 210, or 325 µg/L. There’s no reason to expect that the PUR and Cullighan faucet mounts would perform differently at these concentrations than at the intended ones — these results fit the overall result, which is that carbon filters aren’t good at removing lithium.
You may not be used to seeing scientific papers talk about mistakes the research team made, or the incorrect assumptions that showed up halfway through the project, or the weird random anomaly that doesn’t have an easy explanation. But the truth is that this is just what research looks like.
Academic researchers are expected to pretend like everything went perfectly and nothing weird happened, but this is not how actual research projects work. In real projects, especially where you’re trying to advance the frontiers of knowledge, you have to take chances, make mistakes, and yes, even get messy.
There are always going to be some accidents in any research project, and instead of sweeping them under the rug and pretending we never make mistakes, we’re going to talk about them. This not only is virtuous, it also puts you (readers) in a better position to form your own opinion about our results. It gives you a better sense of what to expect if you want to replicate or extend our results. And if we didn’t tell you about all the SNAFUs, we’d be giving you the wrong idea about what research is really like.
Obviously we want to avoid mistakes when we can, which is why we use techniques like randomizing sample order and including control samples to help prevent and diagnose mistakes. But this sort of thing happens, and it’s in everyone’s best interest to just publicly say “whoops, our bad”.
If you have the time and money, distillation is the best way to get lithium out of your water. The catch is that distillation is slow: distillation machines usually run at less than 1 liter per hour, a small fraction of the speed of other devices, and consume a lot of energy to get there. Distilling all of your cooking and drinking water with one of these machines would be very slow or very expensive or both.
For the average consumer, reverse osmosis is a much better choice. It’s cheaper and faster, and it works nearly as well as distillation does. For the average American, a RO system will ensure that you end up with less than 10 µg/L in your water, probably much less.
Both of the RO systems we tested were under-sink units, meaning they go under your sink (duh) and create a stream of purified water that is separate from the actual tap. That way you wash your dishes with the high flow rate you’re accustomed to from a faucet, but fill your glass or make pasta with the separate stream of RO-filtered water.
You could also spring for a professional-grade household system that filters all the water that comes into your house, but there are a few complications. First off, while it should work basically the same as these under-sink units, we didn’t actually test a household system. Second, it’s got a much higher upfront cost and it would be more of a pain to install and maintain. Also keep in mind that typically only 20-50% of the water entering the RO unit actually leaves as clean, filtered water; the rest never makes it through the filter membrane and goes down the drain. Throwing away that much water for things like showering or washing your car would mean a lot of wasted water.
Finally, a whole-house RO system typically needs to be accompanied by a water softener, and we’re not sure if water softeners contain lithium or not. Water softeners operate by ion exchange, exchanging one Ca2+ or Mg2+ ion for two Na+ ions. You “regenerate” the system every so often by dumping a big bag of rock salt (NaCl or occasionally KCl) into the “brine tank”, which displaces the Ca/Mg off of the ion exchanger. If the salt being used for regeneration contains lithium, it would make its way into the drinking water just as readily as Na+. We haven’t tested any water-softening salt yet (though we might at some point), but we did test table salt as part of another project, and that definitely contains some lithium.
Because of this, it’s not clear whether you’d end up drinking more or less lithium if you install a household RO system with a water softener. If you’re using a water softener without a RO system, you’re probably adding some lithium to your water, though we’re not sure how much.
If you purchase water that was treated by RO or distillation (as many bottled waters are), it’s probably very low in lithium. But the catch here is that many companies put minerals back in, because pure water actually tastes kind of flat and metallic. Aquafina, for example, is first purified through RO before putting a pinch of salt back in for taste. If the pinch of salt contains lithium, you’re back to square one.
Thanks again to our anonymous donors, the Tiny Foundation, Sarah Jantzi, and Whylome for supporting this research. Finally, thank you for reading!
A few people have asked us why we didn’t preregister the analysis for our potato diet study. We think this shows a certain kind of confusion about what preregistration is for, what science is all about, and why we ran the potato diet in the first place.
The early ancestor of preregistration was registration in medical trials, which was introduced to account for publication bias. People worried that if a medical study on a new treatment found that the treatment didn’t work, the results would get memory-holed (and they were probably right). Their fix was to make a registry of medical studies so people could tell which studies got finished as planned and which ones were MIA. In this sense, our original post announcing the potato diet was a registration, because it would have been obvious if we never posted a followup.
Pre-registration as we know it today was invented in response to the replication crisis. Starting around 2011, psychologists started noticing that big papers in their field didn’t replicate, and these uncomfortable observations slowly snowballed into a full-blown crisis (hence “replication crisis”).
Researchers began to rally around a number of ideas for reform, and one of the most popular proposals was preregistration. At the time, many people saw preregistration as a way to save the foundering ship that was psychological science (and all the other ships that looked like they were about to spring a leak).
Calls for preregistration can be found as early as 2013, in places like this open letter to The Guardian, and on the OSF, where people were already talking about encouraging the use of preregistration with snazzy badges like this one:
But despite the early enthusiasm, preregistration is not a universal fix. It has a small number of use cases and those cases are specific. Part of being a good statistician is knowing how to preregister a study and knowing when preregistration applies, and it doesn’t apply all that broadly. We think preregistration has two specific benefits — one to the research team, and one to the audience.
We’ve preregistered studies before, and in our experience, the biggest benefit for researchers is that preregistration encourages you to plan out your analysis in advance. When you do a study without thinking far enough ahead, you sometimes get the data back and you’re like oh shit how do I do this, I wish I had designed the study differently. But by then it’s too late. Preregistration helps with this problem because you have to lay out your whole plan beforehand, which helps you make sure you aren’t missing something obvious. This is pretty handy for the research team because it helps them avoid embarrassing themselves, but it doesn’t mean much for the reader.
The main benefit the audience gets from preregistration is that preregistration makes it clear which analyses were “confirmatory” and which were “exploratory”. Some analyses you plan to do all along (“confirmatory”; no it doesn’t make any sense to us either), and some you only do when you see the data and you’re like, what is this thing here (“exploratory”; you are Vasco da Gama).
This is ok by itself because it does sort of help against p-hacking, which is one of the big causes of the replication crisis. When you do a project, you can analyze the data many different ways, and some of these analyses will look better than others. If you do enough analyses, you’re pretty much guaranteed to find some that look pretty good. This is the logic behind p-hacking, and preregistration makes it harder to p-hack because you theoretically have to tell people what analyses you planned to do from the get-go.
(This only works against p-hacking that comes about as the result of an honest mistake, which is possible. But there’s nothing keeping real fraudsters from collecting data, analyzing it, picking the analysis that looks best, THEN “pre”-registering it, and making it look like they planned those analyses all along. And of course the worst fraudsters of all can just fabricate data.)
But here’s something they don’t always tell you: p-hacking is only an issue if you’re doing research in the narrow range where inferential statistics are actually called for. No p-values, no p-hacking. And while inferential statistics can be handy, you want to avoid doing research in that range whenever possible. If you keep finding yourself reaching for those p-values, something is wrong.
Statistics is useful when a finding looks like it could be the result of noise, but you’re not sure. Let’s say we’re testing a new treatment for a disease. We have a group of 100 patients who get the treatment and a control group of 100 people who don’t get the treatment. If 52/100 people recover when they get the treatment, compared to 42/100 recovering in the control group, it’s hard to tell if the treatment helped, or if the difference is just noise. You can’t tell with just a glance, but a chi-squared test can tell you that p = .013, meaning there’s only a 1.3% chance that we would see something like this from noise alone. In this case, statistics is helpful.
But it would be pointless to run a statistical test if we saw 43/100 people recover with the treatment, compared to 42/100 in the control group. You can tell that this is very consistent with noise (p > .50) just by looking at it. And it would be equally pointless to run a statistical test if we saw 98/100 people recover with the treatment, compared to 42/100 in the control group. You can tell that this is very inconsistent with noise (p < .00000000000001) just by looking at it. If something passes the interocular trauma test (the conclusion hits you between the eyes), you don’t need to pull out the statistics.
If you’re looking at someone else’s data, you may have to pull out the statistics to figure out if something is a real finding or if it’s consistent with just noise. If you’re working with large datasets collected for unrelated reasons, you may need techniques like multiple regression to try to disentangle complex relationships. Or if you specialize in certain methods where collecting data is expensive and/or time-consuming, like fMRI, you may be obliged to use statistics because of your small sample sizes.
But for the average experimentalist, you can get a sense of the effect size from pilot studies, and then you can pick whatever sample size you need to be able to clearly detect that effect. Most experimentalists don’t need p-values, period.
Better yet, you can try to avoid tiny effects, to study effects that are more than medium-sized, bigger than large even. You can choose to study effects that are, in a word, ginormous.
And it’s not like we really care about a simple distinction between working and not-working. The Manhattan Project was an effort to build a ginormous bomb. If the bomb had gone off, but only produced the equivalent of 0.1 kilotons of TNT, it would have “worked”, but it would also have been a major disappointment. When we talk about something being ginormous, we mean it not just working, but REALLY working. On the day of the Trinity test, the assembled scientists took bets on the ultimate yield of the bomb:
Edward Teller was the most optimistic, predicting 45 kilotons of TNT (190 TJ). He wore gloves to protect his hands, and sunglasses underneath the welding goggles that the government had supplied everyone with. Teller was also one of the few scientists to actually watch the test (with eye protection), instead of following orders to lie on the ground with his back turned. He also brought suntan lotion, which he shared with the others.
Others were less optimistic. Ramsey chose zero (a complete dud), Robert Oppenheimer chose 0.3 kilotons of TNT (1.3 TJ), Kistiakowsky 1.4 kilotons of TNT (5.9 TJ), and Bethe chose 8 kilotons of TNT (33 TJ). Rabi, the last to arrive, took 18 kilotons of TNT (75 TJ) by default, which would win him the pool. In a video interview, Bethe stated that his choice of 8 kt was exactly the value calculated by Segrè, and he was swayed by Segrè’s authority over that of a more junior [but unnamed] member of Segrè’s group who had calculated 20 kt. Enrico Fermi offered to take wagers among the top physicists and military present on whether the atmosphere would ignite, and if so whether it would destroy just the state, or incinerate the entire planet.
The ultimate yield was around 25 kilotons. Again, ginormous.
Studying an effect that is truly ginormous makes p-hacking a non-issue. You either see it or you don’t. So does having a sufficiently large sample size. If you have both, fuggedaboudit. Studies like these don’t need pre-registration, because they don’t need inferential statistics. If the suspected effect is really strong, and the study is well-powered, then any finding will be clearly visible in the plots.
This is why we didn’t bother to preregister the potato diet. The case studies we started with suggested the effect size was, to use the current terminology, truly ginormous. Andrew Taylor lost more than 100 lbs over the course of a year. Chris Voigt lost 21 lbs over 60 days. That’s a lot.
If people don’t reliably lose several kilos on the potato diet, then in our minds, the diet doesn’t work. We are not interested in having a fight over a couple of pounds. We are not interested in arguing about if the p-value is .03 or .07 or whatever. If the potato diet doesn’t work huge, we don’t want it. Fortunately it does work huge.
(We didn’t report a test of significance for the potato diet because we don’t think inferential statistics were needed, but if we had, the relevant p-value would be 0.00000000000000022)
What ever happened to looking for things that… work really well. No one has academic debates over whether or not sunscreen works. No one argues about penicillin or the polio vaccine. There was no question that cocaine was a great, exciting, very wonderful local anesthetic. When someone injects cocaine into your cerebrospinal fluid, you fucking know it.
We pine for a time when spirits were brave, men were men, women were men, children were men, various species of moths were men, dogs were geese, and scientists tried to make discoveries that were ginormously effective. Somehow people seem to have forgotten. Why are we looking for things that don’t barely work?
Maybe statistics is to blame. After all, stats is only useful when you’re just on the edge of being able to see an effect or not. Maybe all this statistics training encourages people to go looking for literally the smallest effects that can be detected, since that’s all stats is really good for. But this was a mistake. Pre-statistics scientists had it right. Smoking and lung cancer, top work there, huge effect sizes.
We know not everything worth studying will have a big effect size. Some things that are important are fiddly and hard to detect. We should be on the lookout for drugs that will increase cancer survival rates by 0.5%, or relationships that only come out in datasets with 10,000 observations. We’re not against this; we’ve done this kind of work before and we’ll do it again if we have to.
There’s no shame in tracking down a small effect when there’s nothing else to hunt. But your ancestors hunted big game whenever possible. You should too.
The first time we mentioned the potato diet, in Part III of our seriesA Chemical Hunger, we shared the story of Chris Voigt, the Executive Director of the Washington State Potatoes Commission, who lost 21 pounds on a 60-day potato diet. By Part X of the series, we started to wonder if someone should maybe run a study, and see if the potato diet really works as well as all that.
For those of you who are just joining us, the potato diet is a diet where you try to get most of your calories (>95%) from potatoes. You can have drinks like coffee and tea. You can season the potatoes with salt, spices, and whatever hot sauce you want. You can even cook with oil. The only thing we asked people to entirely avoid was dairy (see original post for details).
Does this mean you can eat fries for every meal? It does, and some people came pretty close to that ideal. See for example, this post:
I have never heard of a diet that allows you to eat french fries for all three meals, and I did just that on a couple of days. It rocked.
As people signed up and started sharing their experiences, we made a twitter thread of live-ish updates. In this thread you can read anecdotes shared on twitter that aren’t found in the official study data.
To sign up for the study, participants filled out a google form (PDF available in the repository; see below) of demographic information, then over the next four weeks, recorded their data on a copy of a google sheet that we provided.
Two hundred and twenty people filled out the signup form before we closed the study. As far as we can tell, most signups came from twitter, reddit, and word-of-mouth. We actually didn’t ask about this, probably should have. Whoops.
We downloaded people’s data when they sent us an email to formally close the study. Anyone who didn’t send us an email to officially close the study, we grabbed their data (if any) in the last days before closing the study. The dataset we’ll be examining today represents the state of the data as of midnight on Friday, July 1st, 2022, four weeks after we closed signups and eight weeks after we started collecting data.
Raw data, the analysis script, and study materials are available on the OSF. We decided to store our data and materials there, since that repository is well-supported and we expect it to stay available for a long time. The organized data is “SMTM Potato Diet Community Trial Main Form.csv”; the script is called “SMTM Potato Diet Community Trial 1 Analysis.R”; and the raw data is in a folder called “Potato Raw Dato”
This dataset is very rich — we certainly haven’t found everything there is to find in these data. A number of people measured other variables (like blood pressure, resting heart rate, and sleep) and we haven’t looked at those data in any systematic way.
Also there is a lot of room for new findings in coding the free-response data. You could, for example, go through and try to code what kind of oil(s) people are using, and see if people who use different oils lose different amounts of weight, find the diet easier, etc.
We really look forward to seeing other people do their own analyses. Send them our way, we’ll link them or do a roundup post or a meta-analysis or something.
Two participants asked that we not share their data publicly. But if you’re following along at home you should still get the same results as we do, because those two participants seem to have entered no data.
If you have advice about what to do differently next time, we are interested in hearing that. But if you don’t like something about the study design and just want to gripe — run your own study!
Let’s start with a recap of the study variables.
Our demographic variables are — age, ethnicity, height in inches, local ZIP or postal code, current country of residence, profession, and reported sex.
Sex was initially reported as “Male”, “Female”, or a free-response “other” field. A few participants reported being trans or nonbinary, so we created two variables, “Chromosomal Sex (estimated)” and “Hormonal Profile (estimated)” where we estimated their chromosomal sex and hormonal profile, respectively, based off of free report data. As the names suggest, these are just estimates. We don’t actually have access to your chromosomes.
This is in case there end up being major endocrinological effects. It seems like there could be sex differences in the potato diet because there are clear sex differences in obesity and in anorexia, which we think may be related.
On their datasheets, participants were asked to record a slate of variables every day. Our main daily variables are — daily weight in pounds; notes for each day; energy for each day on a scale from 1-7, where higher numbers are more energy; mood for each day on a scale from 1-7, where higher numbers are a better mood; and ease of the diet for each day on a scale from 1-7, where higher numbers are finding the diet easier.
We also had a field where participants could record whether or not they broke the diet (eating something substantial other than potatoes) each day. If they stuck to the diet we asked them to put a 0 in this field, if they broke the diet we asked them to put a 1. This is a bit of a mouthful so we will often colloquially refer to these as “cheat days”.
A total of 220 people submitted the initial form.
Of those, 11 people filled out the signup form incorrectly in such a way that we couldn’t sign them up (they didn’t enter an email, didn’t indicate critical data such as height, etc.). We enrolled the remaining 209 people in the study.
Let’s take a look at the demographics of the people who enrolled:
Age ranged from 18 to 69, with a mean of 35.2 and a median of 35.
Reported sex was 50 female, 151 male, 7 other entries (e.g. “non-binary”, “AFAB on testosterone so idk how you wanna categorise that”), and one person who didn’t respond.
Based on this, we estimated 51 XX participants and 156 XY participants; and we estimated 53 people with a more “female” hormonal profile and 153 people with a more “male” hormonal profile.
Reported ethnicity was 185 white, 10 Asian, 2 Indian, and 4 more specific entries (e.g. Latin, Indonesian, etc.). Everyone else who reported ethnicity reported being a mix (e.g. “Brazilian. Mostly white, kinda mixed though.”; “German/Vietnamese/Anglo-Saxon“).
Participants mostly came from the Anglosphere and Europe: 133 US, 17 UK, 17 Canada, 7 Germany, 6 Australia, 4 Ireland, 3 Sweden, 2 Poland, 2 India, 2 Hungary, 2 France, and several singletons from places like Finland, Mexico, Serbia, Brazil, and “Magyarorsz√°g” [sic] which we think is also Hungary.
Profession is hard to code since it’s so diverse, but it looks like the biggest groups were software engineers/programmers, grad students, various scientists and academics, and game designers.
Out of the 209 people signed up, 5 started the diet late for one reason or another, and were still in the middle of the four weeks when we closed data collection on July 1st. We let them keep going and looked at the 204 people remaining.
Of these 204 participants, 44 never entered any data onto their datasheet. As far as we can tell, they just never got around to starting the diet — we certainly didn’t get any data from them.
This leaves us with a total of 160 people who entered some data. Of those 160:
Age ranged from 19 to 61, with a mean of 36.0 and a median of 35.5.
Reported sex was 29 female, 124 male, 6 other entries, and one person who didn’t respond.
Based on this, we estimated 30 XX participants and 129 XY participants; and we estimated 32 people with a more “female” hormonal profile and 126 people with a more “male” hormonal profile.
Reported ethnicity was 145 white, 5 Asian, and 10 other entries like “Polish” or “Japanese/ Hispanic”.
Participants were still largely Americans: 104 US, 13 Canada, 12 UK, 6 Germany, 5 Australia, 3 Sweden, 2 Poland, 2 Ireland, 2 Hungary, and one each to a number of others.
Again the most common profession is software engineer / programmer, with various research jobs and IT jobs behind it.
Of this group, 35 people formally closed the diet early by sending us an email. We coded the reason they dropped out based on their comments.
One we coded as dropping out because of boredom (“Overall not a difficult diet, but I decided to end it because I was getting pretty bored of potatoes.”).
Two reported stopping because they got sick, which we coded as illness. This isn’t potato-related illness, to be clear — one had a throat infection and the other got shingles.
Six reported stopping because of a schedule conflict, coded as schedule. Some of them specifically said they could have kept going otherwise, like participant 66959098:
I am ending my diet at 21 days instead of at 28. This is mostly a scheduling issue, having family visiting next week and would like to go out and eat with them. I believe I could have made the four weeks without too much trouble otherwise, and I may even go back on the diet again sometime later.
The remaining 27 early closures reported stopping because they found the diet really difficult in one way or another, and we coded this as difficulty. For example, participant 29957259:
I threw in the towel on the potato diet six days in. The first few days were easy for me, but it eventually grew much more difficult. I found myself thinking about food way more than someone whose next meal was planned should have.
Clearly the potato diet really does not work for some people! More on this later.
Another 57 people made it partway to 4 weeks but didn’t officially close the study, and we don’t know why. We went back and forth on what to call this, since we don’t know why they stopped reporting their data, and we wanted the coding to sound as neutral as possible. In the end we coded them as dropped.
These participants don’t seem to have just flaked out. Many of them made it a long way. Several people made it past two weeks, and two people made it all the way to day 27:
We’re going to try to stay agnostic about what happened in these cases, because these participants didn’t give us a clear reason why they dropped out. But we can also make some educated guesses.
Some people clearly dropped out because the diet was too difficult. For example, participant 31554252’s last comment was:
Finding it very difficult to keep going—just very sick of potatoes
But other people don’t seem to have found the diet difficult, and probably dropped out for other reasons. For example, participant 71309629 appears to have dropped out because of illness. They said, “Got sick, will update later” on the last day they entered data, and haven’t updated since. We hope you’re ok!
Similarly, participant 97388755 could probably be coded as ending for schedule reasons. She said in the comments:
I renounce potato. I’m moving house and the chocolate cravings and trying to make potatoes for 2 people is a pain in the ass.
It might be interesting to go back and try to re-code all the dropped trials, figure out why they stopped the diet, but not today.
Since we asked everyone how easy the diet was, we can also look at the ease they reported on the last day they gave us a weight measurement (though a few people stopped reporting ease before then). As a reminder, higher numbers / more to the right is more easy:
Some people definitely were finding this difficult when they stopped, and it’s reasonable to think that the people who gave a 1 or 2 on the last day stopped because they couldn’t stand it.
But plenty of people who dropped out without telling us why rated diet ease at a 6 or a 7. The modal value is clearly 5! So while some of these dropped trials are because of difficulty, others presumably dropped out for other reasons: they had to go on a trip, they had a family emergency, they got sick with COVID, etc.
The diet protocol in the original post asked for 29 days of weight measurement. The last measurement would be on the morning of the 29th day, giving us 28 days of complete data.
But we fucked up on the data recording sheet and made it seem like people should record only up to day 28. Most people followed instructions — they gave us 28 days of data, then stopped. This is our fault, we messed up.
To keep things standard, we used each person’s data at day 28 as their final day of data. For people who went past 28 days (a number of people kept collecting their data and/or kept going with the diet), we treated them as if they did 28 days exactly. We used their weight on day 28 as their final weight, counted their number of cheat days up to day 28, etc.
At some point it might be interesting to go back and look at the data of people who did 29+ days, but again, not a project for today.
This is technically 27 full days of potato diet, since the measurement for day 28 is the MORNING of day 28. But tiny differences like this are like, eh, who cares. If the effect is substantial at all, it won’t matter anyways. Anyways, henceforth this span will be referred to as “four weeks”.
One participant (40207077) didn’t report his weight for day 28, so we used his day 29 data. Coincidentally this is also the person who lost the least weight over the 4 weeks. If you kicked him out because he often forgot to report his weight, average weight lost on the diet would be even greater.
Anyways, 64 people made it the full four weeks and completed the potato diet. Let’s review their demographics:
Age ranged from 19 to 61, with a mean of 36.7 and a median of 36.5.
For sex, 5 reported their sex as female, 54 male, 4 other entries, and one nonresponse.
We estimated 6 XX and 57 XY; and we estimated 7 people with a more “female” hormonal profile and 56 people with a more “male” hormonal profile.
For ethnicity, 57 were white, 4 Asian, 1 Polish, 1 “several of the above”, and 1 “half-asian, half-white”.
Participants reported being in the following countries: 46 US, 4 Canada, 2 each in UK, Germany, and Ireland, and several singletons.
Racial diversity is definitely a major limitation of this study, especially since obesity differs a lot across ethnicities. The diet could easily work half as well, or not at all, for African-Americans. Or for all we know, it could work twice as well. The results we have so far look really promising (as you’ll see in a minute), and we think it’s important to see if they’ll generalize. So if we run another potato diet study, and you’re part of a racial group that isn’t well-represented in this study (i.e. if you are not white), your data could contribute a lot!
The first question is, what is the retention rate for the potato diet? Well, it depends how you slice it.
If you want to be maximally strict, 64 people made it four weeks out of 209 enrolled, so 30.6%.
Not too bad. This is a kind of extreme diet, and it would be pretty impressive even if only 30% of people made it to the end. Frankly, we’re impressed so many people signed up in the first place.
But we think this is too low, in fact. Only 209 people were enrolled in the study, and because some trials were ongoing at closing, only 204 had potentially available results. 64 out of 204 would give us a retention rate of 31.4%.
But of those 204 people, 44 never entered any data. There’s a good chance most of these people never started the study, and shouldn’t be considered dropouts. In this case, retention is out of 160, and 64 out of 160 is 40.0%.
If you wanted to be maximally permissive, you could only count the dropouts who sent us an email to formally close the study. This gives us a total of 102 people, and makes the retention rate 64 out of 102 people, which is 62.7%
(Actually if you wanted to be super maximally permissive, you could only count people as dropouts if they explicitly stopped because of finding the diet difficult. Then retention would be 64 out of 91, or 70.3%.)
So we think the retention rate is somewhere between 40.0% and 62.7%, though you could make a case that the retention rate is as low as 30%. In any case, the idea that between one-third and two-thirds of people get to the end of four weeks on basically only potatoes is pretty wild.
Of course, a hard cutoff doesn’t make much sense. Most people made it some number of days between 1 and 28. Heck, five people ended the potato diet on day 27!
When we look at the number of days people made it to, we do seem to see two (or maybe three?) clear groups:
Clearly the most common outcome is to make it the full four weeks. The next most common is to drop out in the first week or so.
But there’s another bump near the end of the third week, and that seems kind of interesting, especially because some people mentioned hitting a wall at around three weeks. For example, participant 23300304 stopped on day 22 and reported:
Initially I found the diet extremely easy… However, quite suddenly after about three weeks I started feeling unwell, with low level nausea, headaches and general tiredness. Initially I thought I was falling ill. But I didn’t really show any specific symptoms of illness. After a few days I was feeling so bad I decided to end the diet. I felt better by the end of the first day eating my usual diet again.
Similarly, things were going great for participant 63746180. They had already lost about 10 pounds over 18 days and seemed to be enjoying it. But then:
My reason for ending is that I was hungry to the point of headache and dizziness, but could not force myself to eat a potato. It was a weird experience, my body was screaming for food but I couldn’t swallow a potato. I went from pretty happy with eating potatoes to completely unwilling to eat a potato in the span of a day.
So there might be something interesting with people hitting a wall at three weeks or so. However, as you can see from the histogram, it was a minority of participants.
4. Weight Loss
Of the participants who made it four weeks, one lost 0 lbs (participant 40207077). Everyone else lost more than that.
The mean amount lost was 10.6 lbs, and the median was 10.0 lbs. The 99% confidence interval on the mean is 12.1 to 9.1 lbs of weight loss. The greatest amount of weight lost was 24.0 lbs, from participant 74282722.
We thought this might end up being bimodal — some people going into potato mode and other people just struggling through — but it looks pretty normally distributed around 10 lbs. There’s sort of a little spike around 15 lbs maybe.
We can also look at individual time series data:
And here’s the average over time:
We can also do these plots as percent weight change, but you’re gonna be pretty disappointed, they look almost exactly the same:
Actually Why Not Just Look at All The Data
Like we mentioned above, a hard cutoff doesn’t make much sense. Let’s just look at all the data.
Here’s weight change by total number of days completed on the potato diet for all participants who entered data:
Seems like a clear trend. And it makes sense to us; if you make it 22 days on the diet, you get about 3/4 the benefit of making it the full four weeks on the diet.
We can see that only two people reported a net weight gain on their diet, and of only 2.3 and 0.1 lbs. In addition, twelve people did report exactly no weight change — though nine of them only entered data for day 1, so they couldn’t have lost any weight. It doesn’t look like the potato diet can go “wrong” and you can gain a lot of weight.
We want to point out that the person who lost the MOST weight (24.8 lbs; participant 71319394) actually ended the diet on day 27 — “I am calling it done a day early, but I think it has gone really well for me and was really easy for about 3 weeks.” — so he doesn’t appear in the “completed four weeks” analyses.
Also note the outlier, participant 89861395, who reported losing 41.6 lbs in 18 days. We assume this is an error, in part because he reported being 296.8 lbs on day 17, and then being 267.0 lbs on day 18, after which point he recorded no further data. It seems unlikely that he lost 29.8 overnight just before closing the study. Probably he lost 11.8 lbs total before stopping, the number suggested by his weigh-in on day 17.
When we plot this over time, it becomes clear that it didn’t really matter if people “finished” or not:
People lost about a half a pound a day on average, though with quite a bit of variation (we did kick out that one measurement claiming to lose 29.8 lbs in a single day, since it’s probably a typo). There appears to be no meaningful difference in the daily weight loss of people who did and didn’t make it the full four weeks. In fact, people who made it the full four weeks had slightly lower average weight loss, a mean of 0.41 lbs a day compared to a mean of 0.55 lbs a day in people who didn’t make it four weeks.
Here’s how the potato diet COULD have worked: some people don’t lose weight, so they quit, and other people do lose weight, so they keep going. If that happened, we would see a really successful group of people who made it to four weeks and lost a bunch of weight, and another group of dropouts who lost little or no weight. But that’s not what happened. Almost everybody who tried the diet seemed to lose about the same amount of weight per day. So something causes the dropouts to drop out, but it’s not that the diet doesn’t work for them. The diet works for pretty much everyone, at least for however long they can stick to it. But then, for unclear reasons, some people hit a wall.
You might want to know, how much weight will I lose if I don’t make it four weeks? How much weight will I lose if I start and keep going until I hit a wall? Well, it depends on how long it takes for you to hit that wall, but we can talk about what you can expect on average.
People who entered at least two weight measurements but didn’t make it four weeks lost an average of 5.5 lbs, with a median of 4.2 lbs and a maximum weight loss of 24.8 lbs.
If we pool everyone who entered at least two weight measurements, they lost an average of 7.7 lbs, with a median of 6.9 lbs and a maximum weight loss of 24.8 lbs.
So strictly speaking, if you start the diet, based on these data you should expect to lose 7.7 lbs on average. If you fully expect to make it four weeks for some reason, then you should expect to lose 10.6 lbs; and if you for some reason are sure you will NOT make it four weeks, you should still expect to lose 5.5 lbs on average.
Finally, it’s worth noting the subjective element. Just look at how happy many participants were with the diet:
I lost almost 25 lbs and have felt great throughout. I have been sleeping fine and having plenty of energy.
Well I thought that was super fun and I’m happy to have done it. Lost about 16 pounds. … Anyway, I had a blast. I would consider doing potatoes again in the future. This is probably the thinnest I’ve been in at least 15 years or so.
Thank you for doing this. I’ve found it very valuable and think potatoes will continue to play a role in my health.
Thanks for organizing this!
Thanks for the opportunity to do this, it’s been an interesting ride, and I did lose weight.
Hi! Thanks for doing such a great study!
I felt really good during the diet. This is the best I’ve felt in several years. My clothes fit better, I’m not as tired all the time, my back and knee has felt better than they had for the last 6 months.
I did it. One month, mostly potato. And I am really happy I came across your tweet about this crazy and kinda dumb idea for a study. Over this past month I lost pretty much exactly 10 kg / 22 lbs. It felt easy most of the time, and I feel fantastic. My goal of a BMI < 30 is still 20 kg away, but that feels achievable for the first time I can remember.
Thanks for running this experiment! It was very fun, and I wish there were more things like this going on in the world.
Thank you so much for including me in your study! It has been a huge boon to me personally and it was nice to be able to contribute to science!
I had a good time overall with the diet, and ultimately I think the viscerally-felt revelation that an adjustment to my diet gives me far greater mental clarity will be long-term life-changing. Thanks for that.
By BMI Bracket
We can also break down these same analyses by starting BMI bracket.
None of our participants were “underweight” (BMI < 18.5) to start. Of the people who entered any data, 27 had starting BMIs between 18.5 and 25, 66 were BMI 25-30, 43 were BMI 30-35, 17 were BMI 35-40, and 7 had starting BMIs above 40.
Retention by Starting BMI
Overall, it doesn’t seem like retention is much better or worse for people with higher or lower starting BMIs. This is a little surprising — you might expect leaner people to drop out more, since they have less to lose. Or you might expect heavier people to drop out more, because they presumably have a harder time losing weight. But we don’t really see much evidence for either.
We can also plot these variables to get a better look. We’ll adapt the colors from this uh lovely diagram by the CDC:
Again, we see pretty similar retention across groups. This plot shows the days completed, out of 28, by people in each bracket. Vertical lines are medians:
People with a BMI < 25 do seem to be more likely to drop out on the first day, but that might just be noise.
And here’s weight loss for people who completed the four weeks by BMI bracket. Again, vertical lines are medians:
As expected, people with higher starting BMIs lost more weight. We can also show this as time series:
What is not expected, and what we find quite surprising, is that people who started the study with a BMI of less than 25 (what they call “normal weight”) often lost weight as well. And not just a little weight, a decent amount of weight. Median weight loss for BMI < 25 was actually 7.3 lbs!
This becomes more striking if we break it out as percent body weight lost:
Nicky isn’t the only example of someone who started with a low BMI and saw it go even lower. There’s also participant 89852176, who made it the full four weeks:
I went into it not feeling like I had a lot of weight to lose (starting weight/BMI 143/21.1), but my wife and I started together at the same time, and she had more to lose. In addition, I was hoping for an improvement in my blood pressure (typically 120ish/85ish); I haven’t seen a significant change there. However, I did see significant weight loss; my ending weight/BMI (this morning, day 29) was 132.4/19.5.
Naturally we are wondering why people who are already at the bottom end of the range for “normal weight” are losing weight on this diet. Two possibilities come to mind.
One possibility is that the natural human BMI is really around 19. These days we think of 22 or 23 as pretty normal, but that seems to be the high end for hunter-gatherers.
Walker and colleagues compiled body size and life history data for more than 20 small-scales societies. They report mean ± SD body mass indices (BMI) of 21.7 ± 2.9 for n = 21 adult female cohorts and 22.2 ± 2.7 for n = 20 male cohorts, mid-range within the WHO category for ‘normal weight’ (BMI: 18.5–24.9; WHO). … within the Hadza hunter-gatherer population, we find little evidence of overweight or obesity. BMI for both men (20.0 ± 1.7, n = 84) and women (20.3 ± 2.4, n = 108) 20 to 81 years remains essentially constant throughout adulthood and similar between sexes (Fig. 1).
The average BMI at 40 years of age [for hunter-gatherers] has typically been around 20 kg/m2 for men and 19 kg/m2 for women. After the age of 40, the BMI for both sexes drops because muscle mass and water content decrease with age and because fat is not increasingly accumulated.
So if the potato diet is resetting your lipostat (if you’re not familiar, we describe this below) and sending your BMI towards what it would have been if you hadn’t been raised in a modern environment, maybe your BMI is headed towards the hunter-gatherer range of 19-20.
It doesn’t seem like potatoes would send your BMI any lower, in part because there have been cultures that lived almost entirely on potatoes and they did not all drop to BMI 10 and die. For example, take this account of the Irish, from Adam Smith of all people (h/t Dwarkesh Patel):
Experience would seem to shew, that the food of the common people in Scotland is not so suitable to the human constitution as that of their neighbours of the same rank in England. But it seems to be otherwise with potatoes. The chairmen, porters, and coal-heavers in London, and those unfortunate women who live by prostitution, the strongest men and the most beautiful women perhaps in the British dominions, are said to be, the greater part of them, from the lowest rank of people in Ireland, who are generally fed with this root. No food can afford a more decisive proof of its nourishing quality, or of its being peculiarly suitable to the health of the human constitution.
Another option is that potatoes just have super weight loss properties that work no matter how much you weigh (but more on this later).
We say “nothing but potatoes”, but the potato diet is actually a lot more permissive than all that. You get oil, spices, and drinks, and in our version of the diet, we said, “Perfect adherence isn’t necessary. If you can’t get potatoes, eat something else rather than go hungry, and pick up the potatoes again when you can.”
People took us at our word, and many people chose to take several cheat meals or cheat days (several people mentioned loving this aspect of the diet). For each day, they reported whether or not they broke the diet, so we have an estimate of how many cheat days each person had, and we can look at that as part of this analysis.
We do want to remind you that this is self-report. Different people had different standards about what counted as breaking the diet, and some people were more rigorous about tracking this variable than others. It might be a good future project to go through all the raw data at some point and get better estimates for adherence based on the comments.
But that said, let’s take a look at them cheat days:
Only five people reported not a single cheat day. Everyone else said they broke the diet at least once. Most people cheated a few times, but a few people (36%) broke the diet for more than a week’s worth of days.
This is important because clearly the potato diet’s effects are robust to a couple’a cheat days.
We can take a better look at this with a nice scatterplot. Here we compare number of cheat days on the x-axis to weight change on the y-axis:
You can see there’s a bit of a trend between more cheat days and less weight loss. Remember, higher numbers here are less weight loss; zero lbs is at the top. People on the left, who cheated very little, lost a whole range of weights. People on the right, who took more than 14 cheat days, tended to see much less weight loss.
The basic correlation is only r = 0.176, and not significant. Though we do notice a weird outlier in the bottom right, and without that participant, the correlation is r = 0.303, p = .014.
One interesting thing here is that the five people who reported 0 cheat days are all tightly clustered around losing 10 lbs, so the diet does seem to maybe be the most reliable for people who don’t take cheat days. But some people who took cheat days lost a lot more than that.
So overall we see that cheat days maybe matter a bit, but not a ton. It’s looking good for the 90% potato diet.
Heck, it’s looking good for the *40%* potato diet! Participant 68030741 broke the diet on 27 out of 28 days. (And actually didn’t mark down if he broke the diet on day 22, so maybe 28 out of 28.) He says:
I couldn’t get enough protein with only potatoes, so I supplemented with other food. Also, eating only potatoes without anything to accompany them quickly became too monotonous for me. So, I ended up getting only 40% of my calories from potatoes, but I still lost 7 lb over 4 weeks. I limited my intake of non-potatoes, but I ate potatoes ad libitum. I didn’t try to limit my daily calories; in fact the opposite, I often just wasn’t hungry enough to eat more.
There are some similar stories from other people, like participant 48507645:
I was really surprised at the results. While I cheated way more often than I wanted or anticipated, I still lost almost 10lbs. That’s with cheating almost every weekend (due to unforeseen social obligations).
And here’s one from participant 35182564:
I also must confess, that I was not very strict with the “no dairy” rule. I took milk for my coffee (4-5 cups a day) and occasionally a small piece of butter or some spoon of plain yogurt to go with the cooked potatoes. This does not seem to have impacted the successful outcome. But it made the diet so much easier and also improved the “empty stomach” and “hungry” feelings a lot. Everything besides these “tiny” amount of dairy, I noted in the sheet.
The most extreme case study may come from Joey “No Floors” Freshwater, who shared his story on twitter. He wasn’t able to enroll in the study proper but he decided to do his own version consisting of “1-1.5lbs of potatoes a day when I could”, or about a 20% potato diet. Turns out it works just fine, for him at least. Here are some screenshots:
So it looks like the 20% potato diet can work, at for least some people.
Most people who made it the four weeks report the diet being anywhere between “pretty easy” and “real easy”.
(24235303) It was remarkably easy to stick to the diet. I generally wasn’t hungry and when I was I just ate a potato. I only had cravings for other things when I was directly looking at them, such as when I was helping to put away groceries for my family. This seemed to require a lot less willpower than my previous successful diets.
(41297226) I lost 17 lbs in 28 days, felt very few food cravings or aversive hunger, didn’t get tired of potatoes.
(14122662) I felt mostly normal during this diet. I did often miss going out to restaurants or just having a non-potato meal, but the craving was never so strong as to be unbearable.
(63746180) Most of the time I had a good experience on the diet. I didn’t feel cravings for other food. Sometimes I would imagine eating out at a restaurant as a fun thing to do, but it didn’t have the same urgency as typical food cravings.
(57747642) General Diet Thoughts: It’s really surprisingly easy. I was skeptical that I’d be able to finish the four weeks when I started, but once you get in the groove (and learn some tricks for prepping large quantities of potatoes quickly and easily) it’s extremely simple to stick with it. I basically never felt hungry or low energy.
Even some people who dropped out mentioned that it wasn’t hard for them. For example, take this report from participant 70325385:
Overall, it was a good experience. I thought getting fewer calories would have a more detrimental effect on my mood and energy, to the point where I wouldn’t be able to function normally at all. What I noticed was mostly a ~2 point penalty to my mood and energy, which isn’t that big in the grand scheme of things but enough to be an annoyance.
On the other hand, we want to note that the potato diet was really, really hard for some people. Here are a few stories from people who stopped before completing four weeks.
(52058043) Not only is it very inconvenient to daily life and travel, it also feels pretty gross. I feel uncomfortably full, but still wanting anything, anything at all, that isn’t potatoes.
(86547222) In short, my experience was not great. First two days I didn’t peel potatoes and my digestion went crazy. After that I started to peel potatoes, which helped but not by a lot. During those 9 days that I stuck to the diet I mostly felt apathy. The diet removed any joy associated with food from my life, and I missed that.
More speculation on some people loving it and other people hating it later.
Beyond the self-report, we can also look at people’s daily ratings of how easy they found the diet, on a 1-7 scale from 1 “hard to eat only potatoes” to 7 “lol this is so easy, I love potato”.
We averaged each person’s ease ratings over the four weeks for a mean ease rating. The mean of these ratings was 4.6 and the median was median 4.7, both of course on a 7-point scale.
It does seem like people who found the diet easier lost a bit more weight:
The correlation here is small, only r = -0.155, and not significant. This may, however, be the result of one participant who lost almost 25 lbs but seems to have hated every day of it. See him in the far bottom left? Without that guy, the correlation is r = -0.326, p = .008.
This is participant 74282722, who is also the outlier on the previous plot, with 23 cheat days out of 28 days of the diet. Perhaps this guy’s experience was not typical.
Comparison to other Diet Studies
It’s not a contest, but we think the potato diet compares pretty favorably to the rest of the literature.
Meta-analyses like this one do find that many diets cause 10-20 lbs of weight loss on average. But these studies tend to run for much longer than the study we’re reporting on today. The studies in that meta-analysis ran for 16-52 weeks (median 24 weeks) to get that 10-20 lbs of weight loss. If the potato diet went for 16-52 weeks… well that would be something wouldn’t it. At an average weight loss rate of half a pound a day, you do the math.
This meta-analysis compared interventions based on diet, exercise, and diet plus exercise found that people lost about 23.5 lbs on just a diet, 6.4 lbs on an exercise regime, and 24.2 lbs with diet plus exercise. Again this is pretty good, but these diets were all run for what they describe as “short durations”, which is 15.6 +/- 0.6 weeks.
This two-year trial from The New England Journal of Medicine compared low-fat, Mediterranean, and low-carbohydrate diets in a randomized design. All three of these diets saw only about 2 kg (4.4 lbs) weight loss at one month. This is less than the potato diet participants who dropped out before reaching four weeks, who lost an average of 5.5 lbs (median 4.2 lbs).
Maximum weight loss on these diets was at around 5 months in, when participants had lost an average of about 5 kg (11.0 lbs) in the low-fat and Mediterranean diets, and an average of about 6.5 kg (14.3 lbs) in the low-carb diet. This is about comparable to the weight loss on the potato diet, but it took five times as long.
The attrition rate for the potato diet is pretty comparable to other diet studies. That NEJM paper mentions that “common limitations of dietary trials include high attrition rates (15 to 50% within a year)”, and as a sampling from some papers we grabbed at random from Google Scholar, we see attrition rates of 49.3% in this study, 32.3% in this study, and 56.3% in this study.
Admittedly these attrition rates are over very different time scales, so it may be the case that the potato diet is a little harder to stick to than these other diets. But that seems pretty well offset by the much faster and more reliable weight loss.
We also didn’t include any of the intense measures many diet studies implement to keep their participants in line. We didn’t lock people in a metabolic ward. We didn’t control how they prepared their meals. We didn’t do portion estimation. Heck, most of our participants didn’t even stick that closely to the diet. Most of them took several cheat days!
They still lost an average of 10.6 lbs over four weeks. Of those who made it the full four weeks, one lost zero pounds — the other 63 all lost at least 3 lbs. Of the participants who entered at least two days of weight data, two gained weight, three saw no weight change, and the other 146 lost weight. If you’re statistically inclined, the effect size for those who made it four weeks is d = 2.28. The potato diet is remarkably consistent.
It’s hard to estimate how much some of these other diet studies cost, but we’d guess at least tens of thousands of dollars. In comparison, our budget was $0. And we did the whole study in what, 10 weeks?
5. Effects other than Weight Loss
Ok, enough about weight loss. We were promised MORE.
The case studies did all mention weight loss, but they also mentioned other beneficial effects, the kind of thing we would love to see.
Chris Voigt reported major improvements in his bloodwork: “My cholesterol went down 67 points, my blood sugar came down and all the other blood chemistry — the iron, the calcium, the protein — all of those either stayed the same or got better.”
Andrew Taylor said, “I’m sleeping better, I no longer have joint pain from old football injuries, I’m full of energy, I have better mental clarity and focus.”
This is pretty exciting, so we wanted to look for other effects beyond weight. To keep things simple, we just asked people to track their mood and energy every day, both on a 1-7 scale (7 is better mood and more energy).
We took a look at both variables, and there does seem to be something there. There’s a small trend for mood, from an average of 4.3 on day 1 to an average of 4.7:
Of the people who made it four weeks, 45.3% reported a higher mood on day 28 than on day 1. An additional 34.0% reported the same mood (on a 7-point scale) on day 1 and day 28.
And slightly more for energy, from an average of 4.1 on day 1 to an average of 4.7 on day 28:
Of the people who made it four weeks, 50.9% reported higher energy on day 28 than on day 1. An additional 37.7% reported the same level of energy (on a 7-point scale) on day 1 and day 28.
But there’s definitely some variation — some people reported feeling VERY energetic:
There were also some reports of more specific forms of feeling energetic, like increased fidgeting:
(81125989) I also noticed I’m fidgeting a lot, but not sure if I was always fidget-y before, and I’m only noticing now since I’ve read about lipostats & Non-Exercise Activity Thermogenesis
(88218660) Definitely had increased fidgeting at various points.
We also did this extremely scientific poll on twitter:
So it does look like a substantial minority experienced this, but still, a minority.
Effects and Variables we Didn’t Ask for
We asked people to track mood and energy; but, perhaps foolishly, we didn’t ask them to track things like blood pressure and sleep.
But despite our failure, many people chose to track additional variables anyways, and reported all kinds of other effects of the potato diet above and beyond weight loss.
Certainly many people did NOT experience these side effects. Many people just didn’t mention whether or not they experienced them, but for most of these effects, there were some people who specifically said they didn’t feel it. For example, participant 81125989, who didn’t feel anything:
I didn’t feel any noticeably better or worse. My sleep, anxiety, & ability to focus were trash the last few weeks, but they’ve already been that way for months before anyway.
But it’s hard to tell for most of these effects, since we didn’t track them systematically. A project for next time (or for one of you!).
Anyways, here is a selection of effects other than weight loss that were mentioned at least a couple times, and/or that we found interesting.
Digestion both Good and Bad
Lots of people reported digestive changes. Some of these were good. Others were very bad.
(72706884) Other: Improved digestion.
(89852176) almost exclusively loose stools alternating with mild constipation from day 12ish onward
(38751343) My only note is that when I ate potatoes for more than 24 hours, I had the best poops. Total no-wipers. 10/10 poops. I have IBS so it’s rare for me to have a solid bowel movement. Next time I decide to have anal sex, I’m definitely going to eat potatoes for 24 hours prior.
Before you go rushing to cram potatoes before your next bout of anal sex, beware: the potato diet gave other people diarrhea:
(68545713) I had trouble getting started with the diet because at first. I was leaving the skins on, and not using any salt or oil. I had quite extreme diarrhea in the beginning, which I attribute to the unusually high fiber. I also just don’t like potatoes, so not using any salt or oil made the actual eating of the potatoes very unpleasant for me.
After only a few days, I allowed myself salt and oil, and at about the same time I started “imperfectly peeling” the potatoes to reduce (but not eliminate) the fiber. This made the diet much easier for me.
Several people reported better sleep, and sometimes reported sleeping more.
(72706884) Improved sleep, even with caffeine pills. I never woke up in the middle of the night, which is atypical.
(34196505) I sort of feel like I slept better. This is not consistent with how I usually feel on a calorie deficit–normally, I have a hard time sleeping.
(31664368) Good energy and sleep from a crappy baseline (~4 month old at home, just starting to get “normal” sleep)
(63173784) I needed more than usual sleep on the diet, but once I added chicken I was able to sleep more deeply
My sleep apnea symptoms disappeared, except when I had the one “normal” meal in the middle. I must be reacting to other foods.
There may be a relationship between the amount of sleep people require on this diet and how much weight they lose — someone should look into this at some point.
Several people tracked their blood pressure, and they tended to see improvement, sometimes a lot of improvement.
If you don’t look at BP measurements very often, here’s a quick refresher on what the different ranges mean, from the FDA:
Normal pressure is 120/80 or lower. Your blood pressure is considered high (stage 1) if it reads 130/80. Stage 2 high blood pressure is 140/90 or higher. If you get a blood pressure reading of 180/110 or higher more than once, seek medical treatment right away. A reading this high is considered “hypertensive crisis.”
Two people saw minor increases. Participant 76703005’s blood pressure went from 123/69 (day 1) to 138/82 (day 29). Similarly, participant 26650045 went from 115/76 (day 1) to 116/80 (day 24, their last day).
But other people saw their blood pressure decline, sometimes by a lot.
(90638348) Blood pressure down, resting pulse down, pulse/ox up (data in spreadsheet)
Looking at the spreadsheet, participant 90638348 saw their blood pressure go from 139/98 on day 3 (the first they recorded) to 122/88 on day 29. They actually have BP data up to day 32, when BP was 125/87
Participant 14558563 also tracked their blood pressure, and found it went from 164/100 (day 5) to 153/98 (day 29). They even have data up to day 35, when it was 150/102.
(68482929) I ate a LOT of seasoning and salt, but my blood pressure dropped to 111/73 (before the diet it was 139/something)
(57747642) My blood pressure went down from a pre-diet average of about 135/85 to an average now of about 128/70. So that’s interesting.
(57875769) I also checked my blood pressure a few times, although I wasn’t scientific about it so I’d consider this anecdotal, but on day two of my diet my blood pressure was 149/96 (yikes!) and my last reading on day 27 was 126/81.
(66959098) I also took a blood pressure measurement before and after the diet, starting at 177/107 and going down to 130/80.
Not asking for blood pressure measurements was an oversight on our part, since the measurement is so standard and it’s so easy to track at home. If we run any future studies, we plan to include it; and if you try the potato diet on your own, we recommend that you track it!
Pulse / RHR
A few people measured their resting heart rate, and found that it dropped during their time on the potato diet.
Participant 90638348 reported their pulse (BPM) dropped from 78 (day 1) to 64 (day 29).
Participant 14558563 reported their pulse dropped from 68 (day 5) to 56 (day 29).
And participant 05999987 had this to say:
I noticed I often had to pee during the night, which is unusual for me. (Note that my version of potato diet was also very low sodium, mostly because bland potato was just fine with me and I figured if I got way out of Na/K balance my body would let me know, like a deer in search of a salt lick). More interesting is my resting heart rate went down by almost 10 bpm from ~63 to 54.
A few people got more comprehensive blood work done, and the changes they saw over the course of the diet were generally positive.
Participant 95730133 had this to say in his closing remarks:
As promised, here’s the results of my blood work! Taken on the first day (5/31) and last day (6/27) of my potato diet. Note the second test was also fasted though it isn’t marked.
Total cholesterol dropped from a high 242 mg/dL to a healthy 183 mg/dL.
LDL cholesterol improved from a high 148 mg/dL to a still high 124 mg/dL (0-99 is the target range).
All other levels remained healthy and in the target ranges.
Another participant (23300304) sent us his full blood test results. Like the guy above, 23300304 saw his total cholesterol drop, from 4.5 mmol/L to 3.1 mmol/L (about 174 mg/dL to 120 mg/L in the other units). He also saw his LDL cholesterol drop from 3.0 mmol/L to 1.4 mmol/L (116 mg/L to 54 mg/L). However, his triglycerides went up, from 0.65 mmol/L to 1.79 mmol/L.
When we tried this diet, we experienced some pretty hardcore hypomania:
This makes sense for us because we are mad scientists. But would “normal” people experience the super-wiring effects of potatoes too? Apparently yes, though certainly not everyone.
Participant 68545713 reported:
Energetically and mentally, I felt very energetic on the diet in a “hectic” kind of way. Not bad at all for me, that’s my preferred state. I tend to think of my mental clarity as being about a) how many trains of thought I can have going at once and b) how often I lose a train of thought to a blank mind. On potatoes, I had all ~3 trains running, and I rarely lost a thought. (That is quite unusual for me, and strikes me as very unlikely to be a coincidence.) … I’d classify the energy I get from a potatoes-only diet as “frantic”, or “hectic”, or “excited”.
Participant 15106191 gave these notes:
(Day 5) Energy boost kicked in today. Feel half my age
(Day 6) Potato energy going strong. Feel like Irish Superman
(Day 15) Almost too much energy, hard to sit down at a computer and work, took a break to play basketball
And participant 02142044 described:
[At] one point, I was feeling a mild euphoria, and then it just stopped … I felt a sort of euphoria/hypomania that lasted from day 17 to day 20, and I’m unsure how to reproduce it
Certainly not everyone saw this effect of the potatoes. Participant 90638348 said:
Never saw the manic energy described by other folks. I was sorta looking forward to that.
Only one person mentioned their migraines, but most participants probably don’t have migraines to begin with, so we found this interesting. This was participant 35182564, who said:
My frequent migraines improved during the diet. I could also go much longer without food than before and the blood sugar ups and downs were less pronounced, which is probably why the migraine is better. I am very happy about that.
Similarly, one person mentioned a serious improvement in their skin. Participant 36634531:
One unexpected consequence is that my skin is way clearer. I usually have a lot of redness in my face and am acne-prone. My skin has been way less red and acne has been infrequent which makes me wonder if I have a food allergy. If relevant for genetic reasons: I am of Jewish and English/Irish descent.
Two people mentioned libido issues; participant 95730133:
My libido was down a good bit this month, which I’ve seen during weight loss periods before.
…and participant 70325385
The diet had a fairly large effect on my energy and mood most days, and greatly decreased libido starting almost immediately.
Most people didn’t report this effect; but also no one mentioned the potato diet making them extra horny.
Fear and Grief???
One of the strangest effects that some people reported was an increase in intense feelings of fear and grief. For example, participant 95730133, who said:
I had 2-3 days with bad anxiety, which is super uncommon for me and represents a big chunk of the days I’ve ever felt anxious. May have had something to do with the rapid weight loss / potatoes.
We also saw some clear anecdotes about this on twitter:
Like I said above, potato diet is fucking weird. I mention this and the above because towards the end of the third week, I found myself crying every day. I was having actual meltdowns… five days in a row.
I am not talking “oh I am so sad, let a single tear roll down my cheek while I stare out of a window on a rainy day” levels of gloom and general depression. I am talking “at one point I couldn’t fold some of my laundry in a way that was acceptable to me, and this made me think I should kill myself, so I started crying”.
Is this a really dark to drop in the middle of a sort of lighthearted post about potato diet? Yes. I am sorry if you are uncomfortable reading it. Personally, I think I have a responsibility to talk about it, because the mentally weird aspect of this diet cannot be stressed enough.
If you experience this kind of side effect, we recommend you dial back or discontinue the diet. As Birb put it:
To anyone who wants to do this diet, or is considering it after the benefits I described above: I encourage you to do it, but please be extra cautious that your mental state might be altered and that you are not necessarily in your right mind.
Muscle / Exercise
Finally, let’s talk about the topic on everyone’s mind: getting swole, and staying that way.
When we opened signups, many people asked if you’d be able to get enough protein on an all-potato diet. Potatoes do have some protein, and more than their reputation would lead you to believe (3-5 g in a medium potato), but it’s true that 20 potatoes a day won’t give you as much protein as many people think you need.
This is where we reveal that this community trial is not actually the first-ever study of an all-potato diet. There are a few very small, very old studies, and they’re pretty illuminating on the subject of potato fitness. Stephan Guyenet explains:
Starting nearly a century ago, a few researchers decided to feed volunteers potato-only diets to achieve various research objectives. The first such experiment was carried out by a Dr. M. Hindhede and published in 1913 (described in 15). Hindhede’s goal was to explore the lower limit of the human protein requirement and the biological quality of potato protein. He fed three healthy adult men almost nothing but potatoes and margarine for 309 days (margarine was not made from hydrogenated seed oils at the time), all while making them do progressively more demanding physical labor. They apparently remained in good physical condition. Here’s a description of one of his volunteers, a Mr. Madsen, from another book (described in 16; thanks to Matt Metzgar):
“In order to test whether it was possible to perform heavy work on a strict potato diet, Mr. Madsen took a place as a farm laborer… His physical condition was excellent. In his book, Dr. Hindhede shows a photograph of Mr. Madsen taken on December 21st, 1912, after he had lived for almost a year entirely on potatoes. This photograph shows a strong, solid, athletic-looking figure, all of whose muscles are well-developed, and without excess fat. …Hindhede had him examined by five physicians, including a diagnostician, a specialist in gastric and intestinal diseases, an X-ray specialist, and a blood specialist. They all pronounced him to be in a state of perfect health.”
Dr. Hindhede discovered that potato protein is high quality, providing all essential amino acids and high digestibility. Potato protein alone is sufficient to sustain an athletic man (although that doesn’t make it optimal). A subsequent potato feeding study published in 1927 confirmed this finding (17). Two volunteers, a man and a woman, ate almost nothing but potatoes with a bit of lard and butter for 5.5 months. The man was an athlete but the woman was sedentary. Body weight and nitrogen balance (reflecting protein gain/loss from the body) remained constant throughout the experiment, indicating that their muscles were not atrophying at any appreciable rate, and they were probably not putting on fat. The investigators remarked:
“The digestion was excellent throughout the experiment and both subjects felt very well. They did not tire of the uniform potato diet and there was no craving for change.”
So previous all-potato diets didn’t lead to serious atrophy; it seems like people can maintain muscle just fine on a potato diet, and maybe even build muscle. Despite being relatively low in protein, that protein may be exceptionally available or otherwise of unusually high quality.
Empirically, participants in our potato study seemed to lose mostly fat, not muscle. Participant 10157137 used a Fitbit Aria scale to measure fat %, which went from 17.3% (day 1) to 16.5% (day 28). And they were not alone:
(57875769) I lost nearly 17 pounds, and if the body composition on my scale is to be believed, roughly 75% of that was fat.
(46804417) In total I lost 12.5lb (5.7kg) and 4.3% (33%->28.7%) body fat. I measured the fat % using a FitBit Aria 2 scale. I found it impressive that almost all the weight I lost was fat, usually when I diet I lose some fat but close to maybe half of the total?
Maybe you don’t trust these home scales, and you know what, fair enough. But these numbers are backed up with athletic performance, which indicates no noticeable muscle loss:
(41297226) Weightlifting: I’ve been lifting off an on the last couple months. Went from deadlift/squat/bench of 155/165/135 on April 29th (day -5 pre-diet) to 160/145/125 on May 16th (day 13, first time lifting during diet) to 175/150/140 (day 21). I’d say: inconclusive, but doesn’t seem like I was held back from improvement by potatoes (+ taking 4g of BCAAs post workout)
(14122662) In general, I was shocked by the amount of weight I lost, especially since I started out slim and didn’t have much weight to lose in the first place. I had to actively make sure I was eating enough each day so that I wouldn’t lose even more weight. That said, I felt fine throughout the diet and stayed physically active by rock climbing, hiking, and playing kickball and tennis. My health was never a big concern for me.
(01772895) I went on several pretty intense road/mountain bike rides and kept up while feeling good over the course of the diet.
(05999987) I stuck with my usual level of physical activity which is at least 5 miles of walking a day, with some plyometrics. On the few occasions I did do some more intensive activities (a hike with a long, steep uphill portion) or jogging I felt more muscularly tired than usual, though in general I had average for me, or slightly above average energy.
(74872365) I felt unable/unwilling to lift weights during it. I was lifting 3x a week beforehand, and tried near the beginning to workout a couple times but started feeling kinds of joint soreness I wasn’t used to (assuming because of impaired recovery from previous workout). I tried to give it a few more days rest and just suddenly felt very much like not exercising… so I hardly lifted at all for the rest of it. But after the diet was over (a few weeks after it, what with moving and stuff) I got back into gym, got going again at reduced weights, and in two weeks matched or exceeded previous personal bests on most lifts (but haven’t gotten back to previous bench press best). I overall feel very positive about the way in which I was able to resume working out and hitting PRs after it was over, it wasn’t an overall bad thing for my lifting in the grand scheme.
On the other hand, not everyone had sustained athletic performance on the potato diet. For example, participant 57747642 said:
One difficulty for me was keeping up my running volume on the diet. Pre-diet I ran ~20 miles a week. During the diet I found longer runs to be extremely tiring–I think I was just in too much of a caloric deficit to have much glycogen available. I started cheating by drinking a bottle of gatorade before my longer runs and that seemed to fix the issue. But I still only averaged about 8 miles a week of running which was quite a step down.
(15106191; Day 14) Bench press went down today, likely losing muscle along with the fat, either because of the low protein of potatoes or just the calorie deficit
(34196505) I lift weights at the gym a few times a week, and even on days when I made a point of eating a ton, I felt more fatigued and had a hard time lifting my goal weight. Physical activity seemed harder in general. This is consistent with how I usually feel about a calorie deficit.
If you’re training for a marathon that’s four weeks away, don’t start now. But for most of us, it’s clear that four weeks of the potato diet doesn’t cause serious atrophy or muscle loss.
6. Why do Some People find the Diet Easy and Others Don’t?
Some people find the diet comically easy, while other people hit a wall at some point and are suddenly unable to eat another potato. We’d like to know why.
It’s worth distinguishing between two things; or that is to say, we think there are two ways to lose weight on the potato diet.
First, you can grit your teeth and force yourself to eat nothing but starchy tubers while fighting back your desire to eat literally anything else. A few people who made it the full four weeks seem to have had this experience. For example, participant 83122914:
It was an interesting experience, but it didn’t feel like any kind of magic bullet for long-term weight loss. I initially ate mostly mashed potatoes, but over time I found myself losing the desire to eat them. I craved meat, salad, etc. … I’ve had similar weight loss results in the past with a low-carb diet.
But most people lost weight the other way: after a day or two of eating potatoes, their appetite waned, they didn’t want anything else, and they began to steadily lose weight.
This is the interesting part. To make this easier to talk about, let’s call it entering “potato mode”, or “potatosis”. Actually, Greek for potato is “patata”, should it be “patataosis”?
Also worth noting that it’s not like the potato diet was just easy for some people and hard for others. More like, almost everyone found it easy at first. Some people found it easy for days or weeks and then suddenly hit a wall. So the question may be more like, why do some people hit a wall at three days, others at three weeks, and others apparently not at all?
It’s possible that the difference between the people who found the diet easy and the people who hit a wall will be something easy to notice, maybe basic demographic variables like race and sex. Let’s see:
The group of participants who provided us any data were mostly male (any way you slice it), mostly white, and mostly from the US.
But overall, basic demographics don’t seem to track onto who made it four weeks and who ended the study early. People who made it four weeks were slightly older, more likely to be from the US, and less likely to be white, but none of these differences are very big.
The only difference that jumps out is by sex. About 20% of the people who got to the point of recording data were female, compared to only about 10% of the people who made it four weeks.
We’re not sure why, or if this is even a real result. With so few female participants to start with, this could just be random noise.
Participants who are XY did report the diet being a little easier, with a mean ease rating of 4.4/7, compared to 4.2/7 for XX participants, but this is not significant (p = 0.530).
We also noticed that XY participants did complete slightly more days overall, but it’s not clear if this is robust. Looking at the plotted data, it doesn’t seem like a huge difference:
The first day of potatoes sucked. I seriously contemplated quitting during the FIRST day. After eating my first round of potatoes, I literally walked from our apartment to a grocery store to look at the extra cheesy hot-and-ready pizza I thought I needed. I gazed at the pizza and walked around the store looking for something to eat. Luckily, I was able to keep it together and walk out of the store and back home to my pantry full of potatoes.
I’m not trying to be dramatic, but it was seriously one of the hardest things I’ve done in my life. It took more will power than I thought either of us had.
But with such a small number of XX participants, it’s hard to be sure.
That said, 20% (6 out of 30) of XX participants made it four weeks. If the potato diet only works for one out of every five people with two X chromosomes, that’s still pretty good.
We do wonder if this is a real effect, and if so, why it happens. It would be good if future studies had more XX participants.
Having lots of trans participants would also help us tell if the cause is more hormonal or more chromosomal. In this study, there aren’t enough people whose chromosomes and hormones don’t “match” to actually disentangle any effects.
Some people seemed to have an easier time, or see better weight loss, when they used less oil.
For our own part, one of us was fine for the first two weeks on a relaxed all-potato diet with olive oil, but didn’t see any weight loss until switching to a no-oil version for the last two weeks, when they lost 10 lbs.
Participant 68482929 did some analysis of his own on this question:
The amount of olive oil I consumed had a noticeable effect on how much weight I lost:
The main thing I craved on the diet was more olive oil. If I ate 10 tbsp / day, that felt about right (and my stool was normal and I gained a bit of weight on those days). The more I cut the oil, the more I had intestinal distress, and the more weight I lost.
Here’s that image:
Participant 88218660 mentioned something similar:
third week – started making air fryer fries at home with < 1 Tbsp of oil and eating pretty much only these. Also allowed myself to have ketchup – I’d estimate an upper bound of 200 calories per day of ketchup, but I expect it was less than that. Stopped losing weight. Very unclear if this is a natural plateau or an actual effect of ketchup. Cravings came back in force, as did normal hunger feeling.
Final day – switched back to mashed potatoes with no oil. Hunger was gone again, cravings were dampened, but didn’t immediately lose any more weight.
It’s not clear if this was the oil or the ketchup (or something else) but they definitely seem to have dropped out of potato mode for some reason. We reached out to participant 88218660 for clarification and he told us that he used olive oil at home.
Despite these stories, many people used lots of oil throughout the diet and still lost weight. This suggests it’s not that all oil is bad and inhibits the potato diet. More likely, it’s that 1) some kinds of oil (e.g. olive oil vs canola oil) inhibit potato mode more than others, 2) certain batches / sources of the same oil (two different brands of canola oil or something) inhibit potato mode for some reason, 3) some people respond to oil differently because of genetics or microbiome or something, or probably 4) some combination of the above. Or it could just be noise, this isn’t strong evidence yet.
Nicky Case also recently did a regression analysis of her own data over 40 days, and found a strong effect of olive oil. But it looks like it was in the opposite direction — for her, more olive oil was associated with more weight loss. Check out the analysis in her twitter thread:
It’s sort of not surprising that all these anecdotes reference olive oil, since we recommended that people should probably use olive oil if they use oil at all. But it’s still kind of interesting. Recommending olive oil might have limited the amount of information we’ll be able to get out of these data! A few people did mention they did very well on Five Guys fries, which are fried in peanut oil… Five Guys, talk to us.
Some people did keep detailed notes of their oil consumption, so it’s possible that a clear answer to this question is hiding somewhere in the data. But it’s also possible that we’d need to run a controlled experiment to figure it out, and we may do that at some point (unless one of you gets to it first?).
Salt / Sodium
Salt intake might also help explain why some people had trouble with this diet.
We didn’t ask people to limit salt intake, but some people may have been keeping their intake down anyways, and that may have made the diet harder than necessary. Even if they weren’t trying to limit how much salt they ate, they may still not have been getting enough. Potatoes by themselves are a naturally low-sodium food.
For example, consider the experience of participant 57875769:
Probably my biggest piece of advice is to use plenty of salt. Depending on the nutrition labels, potatoes have zero sodium or an extremely low amount. It seems hard to get the recommended amount of sodium (and I’ve seen some heterodox sources that say the recommendations should be even twice as high as they are) without adding salt to potatoes. A few days I felt kind of light headed or unfocused and I’d finding adding a little bit of salt to a glass of water (under the threshold where I could taste it) would often improve things pretty quickly.
Or this participant on twitter:
Some people also mentioned craving pickled things, which could be the manifestation of a salt craving:
(01772895) Interestingly toward the end, my main cravings were actually for pickled vegetables for some reason.
Of course, we don’t know for sure if the people who dropped out early WEREN’T getting enough salt. But if some people were avoiding salt this could explain some of the difference.
Another possibility is that finding the potato diet difficult can be an early sign of health issues.
Potatoes are high in potassium, and the kidneys need to do a certain amount of work to clear all that potassium from your system. They’re also high in certain toxins. A healthy body under no extra stress is equipped to handle these toxins no problem. But if your health is compromised, it might be another story.
If you eat one potato, your body will be able to deal with the extra potassium and the low levels of plant toxins. If you eat nothing but potatoes and you have reasonably healthy kidneys, again your body will be able to handle it. But if you eat nothing but potatoes and you have poor kidney health, at some point your poor kidneys may not be able to handle all the extra potassium, potato toxins, and other junk. This will make you start to feel terrible, and may explain why some people did fine on the potato diet for a long time and then suddenly started feeling terrible.
Kidney function seems like the simplest case, but other kinds of hidden health issues could also give your body trouble.
The clearest example comes from Alex Beal (who gave us permission to use his case as an example). He was one of our earliest participants in the potato diet, and also one of the first to drop out of the study. He started tweeting about his experience, did ok on the first meal, but soon found himself feeling awful and totally unable to stand potatoes. He published a log of his experiences here, where he says:
I’ve decided to drop out of the study after less than 48 hours. This diet kicked my ass.
Beal stopped the diet on May 1st. A few days later, he found out he had prediabetes:
This maybe explains why he had such unusual trouble with the potato diet (remember, 90% of people who entered at least one day of data made it more than two days, and 40% made it all the way to day 28). Beal has a (mild) metabolic disorder he didn’t know about when he started, and it’s pretty reasonable to suspect that this may have limited his ability to deal with all these potatoes.
We discussed this with Beal and he agrees it’s plausible. “In a study population of obese folks,” he says, “I do worry undiagnosed diabetes or prediabetes is a risk. It’s very common for it to go undiagnosed.” This is similar to something JP Callaghan mentioned, where he said, “There are tons of people walking around with their kidneys at like 50% or worse who don’t even know it.”
One strike against this explanation is that younger people generally have better kidney function, so if this were why people are dropping out of the study, you’d expect to see many fewer dropouts among younger people, which we don’t see. But for what it’s worth, Alex Beal is pretty young and he had undiagnosed prediabetes before signing up for the study. It’s possible that we recruited a sample that has disproportionately high numbers of young people with undiagnosed renal and/or metabolic disorders.
In any case, finding the potato diet really hard may be an early warning sign for kidney issues and/or diabetes, possibly because the high levels of potassium put a strain on your kidneys that you wouldn’t normally experience, so it might reveal problems you wouldn’t normally notice. So the potato diet may be a useful at-home diagnostic tool.
If you had a hard time with the potato diet, especially if you were only able to make it a few days, talk to your doctor about checking for kidney function and prediabetes.
A number of people mentioned that peeling the potatoes made the diet noticeably easier:
(02142044) The diet was a bit tough at the beginning, probably because I didn’t peel them.
(68545713) After only a few days, I allowed myself salt and oil, and at about the same time I started “imperfectly peeling” the potatoes to reduce (but not eliminate) the fiber. This made the diet much easier for me.
(86547222) First two days I didn’t peel potatoes and my digestion went crazy. After that I started to peel potatoes, which helped but not by a lot.
This matches our experience. On the potato diet, there was a point at which the peels started getting disgusting — but without the peel, potatoes continued to be delicious. We were very pro-peels starting out, but by about halfway through, we started peeling them and that made a clear difference.
This is interesting because it certainly goes against common wisdom about the peels — that they’re especially nutritious, that they’re good for you, and so on. It’s true they’re high in fiber, and it may be fine if you are eating only like, four or five potatoes now and then. But as Stephan Guyenet points out:
Peel [potatoes] before eating if you rely on them as a staple food … Potato peels are nutritious but contain toxins.
Again, your body can handle most vegetable toxins in small doses. But if you are eating a lot, at some point they might get to the point where it’s a problem.
So it could certainly be that past a certain point, eating the peels will become difficult for some people. Or it could be that the peels are generally fine if you’re healthy, but they pose a problem for people with undiagnosed poor kidney function. There could easily be a peels * kidney interaction.
It could also just be fiber. Lots of people reported digestive issues, and the peels are especially high in dietary fiber.
So it’s possible that some people who dropped out early could have made it further if they started peeling their potatoes. If you’re having trouble on the diet, we definitely recommend ditching the peels.
Like we mentioned, potatoes contain toxins, and some potatoes contain more toxins than others. For example, levels of the toxin solanine increase when potatoes are improperly stored, or exposed to too much sunlight, and green potatoes tend to have more solanine.
Most bags of potatoes are fine, but maybe one day you go to the grocery store and just happen to get a bag of greener-than-usual potatoes, which make you feel sick, and since you’re being careful, prompt you to end the diet early. From your perspective you can’t tell why you suddenly got sick, but from a god’s-eye-view, it was the bad batch of potatoes. So maybe random chance is what’s causing some people to hit a wall.
(Just avoiding green potatoes wouldn’t totally fix the problem, because potatoes can be high in toxins without being green. But definitely do avoid green potatoes.)
If this were the case, it would look pretty random who drops out. It does look pretty random who drops out. So maybe the dropouts are from some kind of random factor like this!
7. Why the Heck Does the Potato Diet Work
The human body has a lipostat that regulates body weight, and the lipostat has a setpoint, a weight that it wants to maintain. For the sake of an example, let’s say it wants to maintain a BMI of 23. The lipostat can detect how much fat is stored and takes action to drive body fatness to the set point of BMI = 23. If your body’s BMI is below the setpoint, the lipostat will drive you to eat more, exercise less, sleep more, and store more of what you eat as fat. If your body’s BMI is above the setpoint, the lipostat will drive you to eat less, move and fidget more, and store less of the food you eat as fat.
People become obese because something has gone wrong with the lipostat — for some reason it is defending a set point above BMI 30, and all the regulatory systems of the body are working together to push body weight to that level and keep it there (for more information, see here).
It seems clear to us that something about the potato diet lowers your lipostat set point, and weight loss kicks in because the lipostat starts to defend that new, lower weight.
When you run a normal calorie deficit (don’t eat as many calories as you need), you get sluggish, you lack energy, you get hungry, and you have a hard time exercising. This is because your body wants to defend its weight at the current set point, whatever that point is, and will work really hard to keep you from getting lighter.
But when you are heavier than your current set point, the body pulls out all the stops to help you lose weight and drop to the set point. You feel more energetic, you fidget to burn extra calories, your body temperature goes up, you stop feeling hungry, and so on. In line with this, people in potato mode reported being very energetic, having hypomania, fidgeting all the time, and having no trouble exercising. This is exactly what we’d predict if your lipostat set point suddenly went down.
In addition, there are two special points that strongly support the idea that the potato diet lowers your lipostat set point.
First, some people keep losing weight after stopping the diet. We think this means that the lipostat set point dropped faster than weight loss was able to follow, and it took a few days after the diet was over for BMI to catch up. If the diet just worked on caloric restriction, then you would expect people to start gaining weight again after stopping. But that’s not the case, or at least, not always the case.
(36634531) My weight is still holding steady after resumption of a typical diet. Are you guys going to ping the participants in X months to see if we return to baseline?
(57875769) Since stopping my weight has stayed pretty flat (I was 215.3 lbs this morning and I ended the diet at 215.2, and I was traveling for a few days which usually causes me to gain weight) and I find that I have a much smaller appetite than I used to. I’m having to re-learn how much food I should serve myself or order at each meal because I’m used to eating much more.
This is just suggestive for now, but we’ll know more in 6 months when we do the first followup.
But the biggest sign that the potato diet lowers your lipostat set point is the overwhelmingly common experience of how the potato diet makes hunger feel entirely different.
(36634531) My appetite did eventually tank. I was down to one meal a day. I don’t know if I was just full all the time or if my stomach shrunk or what. I was never feeling hungry throughout the diet.
(68545713) [I] felt less desperate than before-potatoes when I did get hungry. It was wonderful.
(29550957) Subjective feeling is definitely that I could get hungry, but it was not an urgent problem. Completely different from my usual modus operandi of gravitating in the direction of food whenever slightly hungry.
(10010108) I simply was not hungry in the mornings. Once I did start eating, I was starving every 1-2 hours. Out of habit, I do not eat after 8 pm. Sometimes we would have dinner at 7 due to scheduling, and I would be stomach growling hungry at bedtime, between 10-12. I was not going to get up and eat, so I drank water and slept. The hunger just wasn’t there in the mornings though.
(81125989) My sense of hunger was anomalous: some days I’d eat less than 1000 calories and feel totally fine, some days I’d get a sudden sharp pang of hunger right after a hefty meal. And on my cheat days, even when I ate to satiety, I ate a lot less than I did pre-potato diet.
(74872365) I recall feeling like hunger exists in two distinct modes, and potato diet worked helped switch one off while downregulating the other: there’s the “need to feel full and need blood sugar” hunger and the “pleasure reward hunger.” It was like when I finished a mashed potato dinner the first hunger was satiated fully but I still would have eaten a whole pint of ice cream for pleasure if I was allowed to. I still kind of wanted to eat for more pleasure, but the pleasure based eating was “deactivated” from controlling my decision, and the potatoes weren’t hitting that pleasure center. Hence I only ate up to the level of the first hunger metric, the more “physical” one, and that level was downregulated of course. During cheat days (which were all around dinner times I think), the moment I started eating non-potato, I got insanely outlandishly hungry and ate surprising amounts of food the rest of the evening. It was like I would eat a bunch and then suddenly feel empty an hour later.
(68030741) I limited my intake of non-potatoes, but I ate potatoes ad libitum. I didn’t try to limit my daily calories; in fact the opposite, I often just wasn’t hungry enough to eat more.
(1772895) Toward the end of the diet, I found it difficult to eat enough potatoes. I’d be a bit tired and hungry, but the effort of cooking them and eating them seemed too much to bother with. This was an interesting experience, and gave me some empathy for a few of my friends who have a hard time keeping weight on, even with an unrestricted diet. When they’ve described themselves as sometimes being ‘too lazy to eat’ in the past, I basically found that unimaginable, as I don’t think I could ever be too lazy to eat cake, for example. However, if the reward I got from eating cake was similar to the reward I get from eating potatoes, I guess that’s how I’d feel.
What’s interesting though is that I wasn’t feeling tired and hungry and craving some other food — I just didn’t feel like eating. Maybe this is something to do with the stuff Pen Gillette mentioned about eating habits fading. Interestingly toward the end, my main cravings were actually for pickled vegetables for some reason.
(77742719) I did get more tired throughout, and my appetite actually continually decreased. Had to remind myself to eat quite often and actually made a schedule. On this last day, I had only one meal of potatoes, 500 kcal.
(90638348) Was not ever resentful or hungry, always felt “full”
(88218660) First week – no oil, pretty much all mashed, non-organic russets with cajun seasoning and hot sauce. Almost immediately I could tell my cravings were significantly dampened (though not gone, especially if I was looking at tasty food) and that the normal feeling of hunger was entirely gone for me – what was left was a feeling of being almost faint and feeling not great when I went too long without eating. Took a lot of adjusting to.
(57875769) I feel full sooner than I used to, and I feel like there is a much richer variety of sensations that influence whether I want to eat more food. I remember some people advocating that to maintain a healthy weight you just need to learn to listen to my body, which is sort of what this feels like. Perhaps the people giving that advice were always thin and so listening to their body was never hard. I’ve started feeling signals I don’t remember feeling before I started the diet. It’s almost as if the volume from some things (e.g. a hyper-palatable diet) drowned out and deafened me to all the signals I was supposed to listen to. Now I feel like I’m hearing these again.
(76011343) throughout I had a ton more energy, better mood, weird hunger effect that you guys have documented (didn’t feel hungry and had to force self to eat)
As you can probably tell, this experience was extremely common. But we should note that it wasn’t universal, even among people who lost a lot of weight. Participant 99479977 lost 22lbs but specifically mentioned no appetite/hunger effect:
I’ve seen a lot of people mentioning how the diet changed their perception of hunger. For me at least that didn’t change. What I did notice though is that I become sated much quicker. Today I packed myself four medium size roasted potatoes for lunch during uni, and I felt sated after just three of them.
And see also this report from participant 34196505:
It wasn’t like some hunger switch flipped off in my brain after a day or three of nothing but baked potatoes–I still got hungry, and it felt similar to normal hunger. I saw people on twitter saying they were having a hard time reaching 1,000 calories a day. Can’t relate.
People did eat very few calories on this diet. Most people didn’t track calories very closely (another benefit of the diet — no calorie counting!) but some people chose to record how much they were eating. The people who recorded calories (self-report, so grain of salt here) generally reported eating very little.
For example, participant 68030741 kept super detailed notes on calorie consumption and should be the starting point for anyone who wants to dive deeper into this question. He reports eating as little as 756 calories in a given day, and never more than 1740.
Participant 71309629 never reported eating more than 1556 kcal, and ate as little as 307 kcal one day.
Participant 07644625 has “been tracking [calories] for 4035 days … hard to stop now” and reported eating as little as 1172 kcal in a day — but also often ate more than 2000.
Participant 05999987 also said:
As for ease of diet, it was quite easy to feel full, without eating very many calories at all. This worried me the first week, even on days when I supplemented the potatoes with salmon I never ate even 1300 calories a day. In fact, I averaged 921 calories per day.
This is consistent with the reduced appetite. But it is NOT an explanation any more than “the bullet” is a good explanation for “who killed the mayor?” Something about the potato diet lowered people’s lipostat set point, which reduced their appetite, which yes made them eat fewer calories, which was part of what led them to lose weight. Yes, “fewer kcal/day” is somewhere in the causal chain. No, it is not an explanation.
But we’re bored of trying to explain this one, so we’re going to let the cat do it:
Alternately, if you prefer your arguments to come from bipeds:
But that’s ok, this study was not designed to help distinguish between different theories of the obesity epidemic — it was designed to see if the potato diet works under realistic conditions, and to get a rough sense of what percent of people it works for. Now that we have that, future studies can use the potato diet as a “model diet” to start pitting theories against one another. Won’t that be fun.
Even so, the data from this first study does tell us a little bit about different theories. Compared to other diet studies, the potato diet has the benefit of being super controlled — it’s a clear baseline of potato, with few interfering factors. So let’s take a look.
Something special about potatoes?
One thing we need to address right off the bat is the possibility that potatoes cure obesity for some reason totally unrelated to the obesity epidemic.
For example: cocaine makes you lose weight. But the obesity epidemic didn’t happen because everyone was on cocaine for all of history, which kept them skinny, and then in the 20th century people started forgetting to take their cocaine, and we all gained 40 lbs. It’s just that cocaine has strong weight loss effects totally unrelated to whatever caused the obesity epidemic.
Similarly, it’s possible that potatoes are just a potent weight-loss drug for reasons totally unrelated to the increase in obesity since circa 1970. There are a few things that make this seem plausible.
For starters, Staffan Lindeberg, in his book Food and Western Disease, has a whole section on how maybe humans were built to eat roots and tubers:
Increasing evidence suggests that large starchy underground storage organs (roots, tubers, bulbs and corms), which plants form in dry climates, were staple foods 1–2 million years ago. There are at least three arguments in favour of this notion. Firstly, in contrast to most other animals including non-human primates, humans have an exceptional capacity to produce salivary amylase in order to begin hydrolysis of starch in the mouth. The underlying change in copy number of the gene coding for salivary amylase may have occurred approximately 1 million years ago. … Secondly, roots often need to be prepared under high temperature in order for its starch to be available for digestion and for its bioactive or toxic substances to be neutralised. There are many indications of Palaeolithic humans using fire for cooking, and one of the most common cooking methods for plant foods was probably the so-called earth oven, where food wrapped in large leaves is placed in a covered pit with hot stones or glowing coals. Thirdly, human tooth morphology, including incisal orientation, seems to be well designed for chewing root vegetables. … Our bipedal ancestors were apparently less efficient hunters than many carnivorous animals and less efficient fruit-foragers than the arboreal primates. In order to increase the caloric yield per workload (‘optimal foraging strategy’), root vegetables may often have been an optimal dietary choice. An illustrative example is the Machiguenga tribe of the Amazon, among whom one woman can dig up enough root vegetables in one hour to feed 25 adults for one day. The excellent health status among this and other starch-eating ethnic groups, including our own study population in Papua New Guinea (see Section 4.1), contradicts the popular notion that such foods are a cause of obesity and type 2 diabetes.
If we really are built to eat tubers above and beyond all other foods, this might explain why the potato diet lowers your lipostat set point to hunter-gatherer levels.
There’s also some evidence that potato protease inhibitor II suppresses appetite and reduces food intake, though these studies don’t seem to be especially targeted — it looks like they basically just gave people potato extract.
We don’t think the evidence is all that strong, but it certainly seems possible that potatoes just suppress appetite and make you lose weight.
We’ll know more when we get the six-month followup results. If potatoes just suppress your appetite during the time you’re eating them, then once you stop eating them, you should gain most of the weight back. But if potatoes are doing something more profound, and resetting your lipostat or whatever (however they do that), then weight loss should be at least somewhat sustained by six months out. For what it’s worth, this is what we see in the case studies, like Penn Jillette and Andrew Taylor, who seem to have had little trouble keeping the weight off.
It’s possible of course that BOTH are true, that potatoes both suppress your appetite in the short term and somehow reset your lipostat in the long term. In fact, the combination of these effects would be a pretty good explanation for why the potato diet is so unusually powerful. But we’ll have to wait and see.
But assuming for a moment that potatoes are NOT a superpotent weight-loss drug for some reason, what would this tell us about other theories?
Calorie-Counting, Willpower, and other Traditional Diets
(34459757) Pretty easy as far as diets go, basically never felt hungry. Previously I’ve successfully lost 25 lbs via just calorie restriction (mostly by eating box mac and cheese and other prepackaged things with easy calorie counts), and potatoes were definitely easier and I lost weight at the same speed.
(66959098) It felt pretty easy. I have tried simple CICO diets before where I simply reduce portion sizes and maintain a calorie deficit, which were incredibly hard to follow through and caused me to think about food all of the time. This had no such effect, no strong hunger, no strong cravings. I am happy with the results from just three weeks.
(99479977) I have tried various diets before, but restricting calories while eating whatever I like left me hungry, which lead to overeating and actually gaining more weight. The potato diet kept me sated, allows for just enough variety (especially through condiments) to keep me engaged
(27316026) I started the study slightly overweight by BMI and mostly interested in helping out along with seeing how it went firsthand. I’m 35 and 5’9 and my weight has been slowly going up on average for a decade, interrupted by harsh diets every few years to try and get back down under 160. I’ve always succeeded at these diets, which normally lasted around 2 months and involved meticulous calorie counting. I hated these diets and was only able to maintain them with the knowledge that they would be over relatively soon. Comparatively the potato diet has been a joy. It only took a few days to settle into, but after working out a few dishes I enjoyed I wasn’t hungry and food cravings were largely absent.
(95730133) I was pleasantly surprised with the amount and consistency of weight loss on this. 2.5 lbs a week is pretty dramatic and this was even easier to stick to than when I’ve done calorie counting previously at a shallower slope (1.25 lbs/week).
(29550957) This is pretty much the best diet I’ve ever been on, including earlier this year when I also ate mostly potatoes- but with tons of dairy (butter, sour cream, cheese) on them. Despite literally messing up an entire week’s worth of days, I seem to be durably down about 10lbs.
(30719090) This has been quite a revelation:
I have been dieting on and off for about 10 years now. The only successful diet was 10 years ago when I got down to 75kg (165lbs). This was based on buying an expensive range of low carb meals. I was less overweight at the time and it was something of a struggle. The diet was eventually derailed by personal circumstances and I have since then gradually increased my weight reaching 200lbs and over recently.
All other diets I have tried have had a small loss initially, but the loss has never continued. The psychological difficulty of maintaining a restricted diet when the losses did not continue was always too much for me. I hate the feeling of being hungry.
The potato diet has been very different. I actually like potatoes so I have not found it difficult to eat them every day and I have found it very easy to resist the temptation of other food.
(35182564) Since I was very successful, losing more than 20 pounds in six weeks, I will probably continue some more relaxed form of the diet for a few more weeks. I have been trying to lose weight for years with absolutely no success. The potato diet did in six weeks, what I could not accomplish in many years. I hope I can keep the lower weight (will send an update in a few months).
(05999987) As a person who has slowly gained weight over the years until I hit the border BMI between overweight and obese and it has become very difficult to lose weight. I’ve often done a couple weeks of limiting to 1500 kCal/day with what a normal person would think healthy–lots of vegetables, some whole grains, some lean proteins, olive oil, legumes. Every time I’d lose a couple pounds, but not much more, and find myself to be quite hungry most of the time. The main difference with potato diet is that I only once experienced the brain-crashing feeling that I need to eat something immediately because my brain is no longer working due to the colloquial usage of “low blood sugar”. The rational part of my brain also didn’t notice any hunger and I could read about/watch people eat/think about delicious foods and not feel like I really wanted to eat them, and I’m the sort of person who thinks about cooking a lot. Plain cold potato was just fine with me, and while I looked forward to the end of the diet and eating normal food again on a theoretical level, I didn’t care about adding condiments, etc.
(63833277) I occasionally had french fries or tater tots or even a couple of times pringles. My wife used some dairy in preparing the mashed potatoes and had ketchup on my fried potatoes, so probably technically every single day should have a “1” in the “broke diet” field. But if I’d done that I’d never have been able to stick with it as well as I did–I basically tried to bend the diet such that I could successfully stick with it but no further and call that success. I thought about retrospectively changing them all to 1s but there *were* days when I *actually* broke the looser diet I’d set for myself and I didn’t want to elide that distinction. Basically think of my diet as a slightly loose potato diet that’s like 95%-97% potatoes instead of 97%-99% as expected. Sorry for not being ideal about that, I figured that would be better than giving up after 5 days.
DESPITE THE DEVIATIONS, THE DIET WAS AN ASTOUNDING SUCCESS!
I’ve never lost weight before. My life has been a slow drumbeat of “this is my setpoint weight, I can’t lose any but I don’t gain any” punctuated by “Life event, my setpoint weight is now X lbs higher than it used to be”. I was never able to motivate myself to stick with diets because I was constantly half-assing them, thus not losing weight, thus seeing no point in sticking with a diet that wasn’t losing me weight.
I lost half a pound a day on this potato diet. I am astounded, as is everyone who knows me!
The potato diet is not a willpower diet. Some people saw huge effects even while cheating. Some people saw huge effects on this diet even when they had found other diets super hard in the past.
We understand if you don’t really get this. We didn’t get it either, despite reading about all the previous success stories, until one of us tried the potato diet for ourselves. Hunger vanishes in a really weird way that is hard to describe to anyone who hasn’t felt it directly. So listen to all our participants who are like “no it’s not calories, it’s not willpower”. Or try it for yourself, you might be surprised!
Anyone else who complains about calorie-counting will be thrown directly into the sun.
Carbs make you fat
Some people think that carbs make you fat. But the potato diet seems like bad news for any “carbs make you fat” theory, since potatoes are starchy carbs. More complex versions might still have a leg to stand on, but obviously this finding is a problem for this kind of theory.
We didn’t track the oil people were eating in any rigorous way, but many people had seed oils like canola and peanut oil on their potatoes. Since their diet was otherwise so limited, this seems like a problem for seed oils theory.
On the other hand, the amount of oil they were eating did seem to make a difference for some people. So maybe this is more evidence for “something that is sometimes in oil and sometimes not”. It fits pretty well with contamination theories (more in a bit), or anything else that might vary in oils, perhaps due to factors like different growing conditions.
There are some theories that suggest that the obesity epidemic is the result of what we’ll call “long-term” factors. For example, evolutionary theories say that natural selection is, for some reason, pushing us towards greater body weights over time. Epigenetic theories suggest that things that happened to your parents or grandparents cause obesity, as the result of gene expression.
Developmental theories say that people become more obese later in life because of something that happened to them early on in development or childhood. This recent massive review paper specifically argues “that obesity likely has origins in utero,” i.e. you get obese at 25 because of things that happened to you when you were an embryo.
But the potato diet poses a challenge for these theories. If obesity is caused by something that happened to you in utero, or by something that happened to your grandmother, then how come it can be reversed in a couple of weeks of potatoes? There may be ways to resolve this challenge, but it’s a challenge nonetheless.
Some people have told us, “oh you can eat any one thing and lose weight like this”. Penn Jillette also says this. He told “Good Morning America” in 2016:
It didn’t have to be potatoes, they aren’t magic. I picked potatoes because it’s the funniest word. I could have chosen beans or just almost anything.
We’re not so sure. In particular, why do people think that other mono diets work? We haven’t seen any. We encourage anyone to find anecdotes, studies, or better yet, run their own Onion Diet study or whatever.
The potato diet isn’t even really a mono diet. We explicitly allow for oil and seasonings, and lots of people lost weight with tons of cheat days. The mono-ness (monotony?) of the potato diet clearly is not the active ingredient.
Potatoes are also unusual in that they are (almost) nutritionally complete. You couldn’t do the white bread diet and get far. But you could maaaaaaaybe do the whole wheat bread and oil diet, or the wheat bread and cheese diet. Also known as: the basic daily diet in Europe for centuries.
That said, we do think that studies (maybe more internet community trials) of other very simple diets would be interesting — especially since most cultures historically have had very simple diets, which shows there are many simple diets you should be able to live on indefinitely. So we’d love to see, for example, studies on diets composed exclusively of:
Rice & beans
Rice & fish
Rice & lentils
Buckwheat soba & edamame
Bread & olives / olive oil
(Someone should check that these are nutritionally complete first, though.)
This last one is already close to the Mediterranean diet, but it would be interesting to cut the Mediterranean diet down to literally just bread, olives, olive oil, wine, and cheese. Or literally to just bread and olives / olive oil, if you could survive on that.
So anyways, if you are sure that any mono diet would work, please do run your own study, we want to see it. We’d be happy to discuss study design with you!
Some people put the obesity epidemic down to a factor called “food reward”. They say that people are obese now because food has gotten more delicious, and that the potato diet causes weight loss because potatoes aren’t delicious. An attempt to describe the theory might look something like this:
People are more obese because food is way more fun to eat now. You can even be agnostic about why food is more fun to eat, and maybe it’s a million small reasons. But over time food producers have figured out how to hit that mental g-spot that makes people go YUM, and when you do that, people eat more than they should and they gain weight. The potato diet works because potatoes are boring and so people don’t overeat.
To be frank, we still don’t really get this theory. That is, we don’t think it makes sense.
First, we’re not convinced modern food is more delicious than old-timey foods. They had butter and ham and sugar and ice cream and even donuts back in 1900. Check out our review of foods of the 1920s and 1930s — lots of the food culture was weird, but they also had like, just tons of lard and pie.
Second, if the problem is that Doritos and Kraft Singles have been hyper-engineered by food scientists to be irresistible, then how exactly would the potato diet pry people away from them? If they are irresistible, then it should be really really hard to stop eating doritos and start eating potatoes. But people say that it doesn’t take much or even any willpower to stay on the potato diet, and many people report no cravings. If your model is “people eat the most delicious foods available and cannot help themselves”, then the only way the potato diet could hold people’s attention is if straight potatoes are more delicious and addictive than twinkies.
Frankly we think they are more delicious than twinkies — but if that’s true and food reward is the law of the brain, then fast-food companies should be peddling baked potatoes instead of Snickers bars.
Finally, the food reward perspective predicts that the potato diet works because potatoes are boring so you don’t want to eat them. We think this is also bunkum. Potatoes are great, and everyone knows it. Lots of participants reported not only enjoying potatoes, but liking them more after completing four weeks of the study:
(24235303) I didn’t mind eating potatoes. They were still perfectly tasty throughout, and varying form factor and spices kept things fresh enough.
(02142044) I felt a sort of euphoria/hypomania that lasted from day 17 to day 20, and I’m unsure how to reproduce it … It was both a feeling of well-being, but also the potatoes started feeling delicious, like they were extremely savory.
(29550957) The last two days my family forced me to eat a bunch of other stuff for my birthday and honestly I wasn’t super enthusiastic about it! I wish I could have just been eating more potatoes. I notice I definitely felt worse after eating stuff like cake, and actually felt durably very stuffed for hours afterwards.
(31497197) Overall, I’d say the diet “works” in that I ate as much as I wanted, mostly didn’t crave other food too often, never got sick of potato, and lost weight. On the very relaxed diet, I lost an average of 2lbs/week, and I think that would have been higher with less frying, but commercial food is not conducive to diets at the best of times. … This is really easy, in that I don’t hate potatoes and haven’t gotten sick of them.
(16832193) I was quite surprised that I didn’t get tired of potatoes. I still love them, maybe even more so than usual?!
Participant 57875769, Day 11:
My wife and I went out to eat with a friend and I expected to use today as a cheat day, but honestly potatoes sounded like the best thing on the menu so I ordered hash browns and french fries. The hash browns were very filling on their own so I didn’t eat many of the fries.
And again Day 29:
I’m ending today. It’s weird though, I’m thinking of all the foods I could eat today and I might just stick with potatoes for a lot of my meals. It’s going to feel strange going back to a more varied diet.
So, people come out of the diet saying they love potatoes. Many of them choose to keep eating potatoes even though they’re off the diet. Some of them say they MISS eating so many potatoes. If this isn’t what people mean by “food reward” or “palatability”, then we’re not sure what they mean. If people do mean something else specific, we’d be interested in hearing that.
Same thing for satiety. Yes, potatoes are high satiety, in the sense that you don’t want to eat anything else after you eat potatoes. But why are they high in satiety? Why do they make you not want to eat any more? This is borderline circular reasoning.
Some people think that the obesity epidemic is caused by some kind of problem with the microbiome, the little beasties that live in your digestive system.
This is really a proposed mechanism, rather than a theory of the cause(s) of the obesity epidemic. It doesn’t explain why the microbiome gets so messed up in the modern environment, but this also means it is potentially consistent with many different theories. If high levels of sugar, fat, light exposure, iron supplements, PFAS, lithium, processed foods, or whatever mess up the microbiome, and something in potatoes fixes it, the potato diet would work just about like we see here.
This seems reasonably plausible to us. In particular, many participants report digestive or gastrointestinal changes (both good and bad) on the potato diet, which is about what you would expect if the potato diet were seriously changing your microbiome. One possible limitation is that weight loss does seem to be driven by the brain, but there may be a gut-brain connection that renders this point moot.
That said, we’re not sure how to test this hypothesis any further. We could compare the potato diet to a normal diet supplemented with potato starch, but if the potato starch supplement also caused weight loss, that wouldn’t point to the microbiome specifically, it would just show that the potato starch contains the same active ingredient as the potato diet, whatever that is.
We could also test stool samples, but honestly we don’t know what we would be looking for. Yeah some things would probably change in your microbiome after four weeks of potatoes, and we could see if any of them were correlated with weight loss, but that’s a pretty blunt instrument. What should we actually look for? If anyone has opinions on *exactly* what might be going on with the microbiome, we’d be interested in hearing your theory.
“Processed food makes us fat” is a line that has been pushed by outlets such as the Washington Post and the NIH. The basic idea is pretty simple: ultra-processed foods make you fat, for some reason. People who support this perspective don’t usually say what it is about these processed foods that make them so fattening, but it’s often mindlessly conflated with the food reward theory:
It also doesn’t mean that all processed food is bad. Whole-grain bread and cereal are excellent, and there are good versions of such things as frozen pizza and jarred pasta sauce. Also wine.
What it does mean is that modern industrial food processing — and only modern industrial food processing — has enabled the manufacture of the cheap, convenient, calorie-dense foods engineered to appeal to us that have become staples of our obesogenic diet.
This perspective does seem to predict that the potato diet should cause weight loss, because potatoes are super unprocessed, about the rawest food most people are likely to eat. Participant 20943794 does a nice job pointing out just how unusual potatoes are in this way:
Potatoes are a lot less processed than most food I eat … even the dishes I “make” “myself” have a big pre-made components. For example, when I “make” spaghetti, I used dried noodles that were made in a factory, a jar of sauce that was made in a factory, and beef that was butchered in ground in (at least) an industrial kitchen, if not another factory. The only stuff that’s really raw is the vegetables I chop and add.
So at first glance, the potato diet looks good for the idea that processed foods make you fat.
But there are some problems. First off, even if processed foods make you gain weight, that doesn’t necessarily mean that unprocessed foods will make you lose weight. Foods high in cyanide will kill you, but foods low in cyanide won’t bring you back to life (as far as we know, maybe someone should check).
We also want to say, we really think this is a non-theory. Even assuming processed foods do make you fat, this isn’t a theory (in our opinion) because it doesn’t address the question of WHY processed foods make you gain weight.
For comparison: in this study, we’ve found that eating enough potatoes makes you lose weight. But “the potato theory” isn’t a good explanation for the potato diet; we want to know what about potatoes makes this happen! So we really demand to know what it is about processed food that (potentially) makes people gain weight. Treating “processed foods” as a theory itself is at best circular reasoning (“processed foods make you fat because they are processed foods”).
Not to say that there aren’t potential versions of this idea that do work as a theory. Processed foods might be uniquely low in nutrients that we need to stay lean (potassium?). Or, since they spend so much time in contact with industrial machinery, they might be especially high in obesogenic contaminants.
There are all kinds of contaminants in the environment that didn’t used to be there. We know that some chemicals can cause weight gain in humans and animals. With these two facts in mind, we think it stands to reason that the obesity epidemic could be caused by one or more contaminants that are getting into our brains and messing up our ability to properly regulate our body weight. We presented a version of this theory in our book/series A Chemical Hunger, and while we don’t think it’s a sure thing, we do think that there’s a lot of evidence in favor.
The potato diet is definitely consistent with the contamination theory. Since potatoes are so incredibly unprocessed, they are presumably unusually low in most contaminants. Whatever contaminant you might be concerned about, there is probably less in a plain baked potato than there is in a steak, candy bar, or box of pasta.
The main wrinkle here is that weight loss on the potato diet is so fast, which is a little weird if we assume that the obesity epidemic is caused by contaminants. It seems like something about the potatoes would have to either stop the contaminants from messing with your lipostat, or would have to rapidly flush the contaminants from your body.
Briefly, the lithium hypothesis looks plausible because lithium causes weight gain at clinical doses, and we know people are exposed to more lithium now than they were back in the 1960s. The only thing is, how much lithium do you need to get exposed to before you start gaining weight, and are we getting exposed to at least that much? We’re working on answering these questions, but we have found some evidence that people get exposed to quite a bit in their food (though it’s complicated).
The fact that the potato diet causes weight loss isn’t really strong evidence for or against the lithium hypothesis. But we do want to point out, it’s consistent with the lithium hypothesis.
Potatoes are high in potassium, and there’s evidence that potassium competes with lithium in the brain in interesting ways. If obesity is caused by your brain getting all gummed up with lithium, and potassium makes it stop, then the high levels of potassium in potatoes would be the sort of thing that might cause lots of rapid weight loss.
Participant 02142044 mentioned this hypothesis:
You probably already know this, but I find it credible a potential reason as to why the diet works, if it does, is that it is helping clear lithium, which would also help explain the mild hypomanias people experience. https://jasn.asnjournals.org/content/10/3/666 seems to indicate that potassium and sodium can help with clearing lithium. That is also why I started salting more.
The fact that the potato diet causes hypomania in some people and fear & grief effects in others is also maybe consistent with lithium, since lithium is both an antimanic and a sedative.
Another mark in favor is that we do have some idea of what foods may be high in lithium, and there are a few hints that these foods can boot people out of potato mode and stop their weight loss. In particular, we have reason to think that tomatoes are often high in lithium, and one of our participants reported this:
Another food group that we think is often high in lithium is dairy, and there’s again some evidence that eating dairy can limit the potato diet. Consider this story from participant 29550957:
This is pretty much the best diet I’ve ever been on, including earlier this year when I also ate mostly potatoes- but with tons of dairy (butter, sour cream, cheese) on them. Despite literally messing up an entire week’s worth of days, I seem to be durably down about 10lbs.
If this is the case, then cheating on foods that are low in lithium should always be fine, and may explain why people were able to cheat on this diet so much and still see the effects.
Cheating on foods that CAN be high in lithium is a gamble. A crop that concentrates lithium won’t grab much if it’s grown in a lithium-poor environment, but will be totally loaded if it’s grown in a lithium-rich environment. So it’s quite possible that that e.g. some ketchup is loaded with lithium and some isn’t, depending on where it was grown, how it was processed, etc. This would look like ketchup making a huge difference for some people and not at all for others.
Unfortunately we still don’t have a great list of which foods are high and which are low in lithium. The list we do have, we don’t particularly trust, which is why we are gonna do our own survey of the food supply.
However if we had to guess right now, our best bets for foods that are high in lithium (and if this hypothesis is correct, might inhibit the potato diet) are: Eggs, milk, soft cheeses (but maybe not butter or hard cheese?), anything containing whey, tomatoes, goji berries, leafy greens, beef, pork, carrots, and beets. But again, this list ain’t gospel.
If the lithium-potassium competition hypothesis is true, other high-potassium, low-lithium diets might also cause weight loss. There’s a little bit of evidence that potassium consumption is related to successful weight loss, which makes this seem plausible.
But straight potassium supplementation may or may not work. At first we thought you could just give people potassium salt and see what happened, but we talked to a specialist who studies lithium clearance from the brain, and he said that the bioavailability of potassium from different sources complicates this a lot. We’re still trying to figure out what a good design for this study would be, but it’s not necessarily as simple as “consume a lot of potassium, avoid tomatoes and whey, and lose a lot of weight”, though we suppose someone could try it and see.
Looking at lithium and potassium in the urine of someone doing the potato diet might help with this, and so we’re considering asking for urine samples in future studies. But it might also be inconclusive.
For example, maybe lithium raises your lipostat set point by gumming up the brain somehow, and high levels of potassium lower the set point by increasing lithium clearance and forcing it all out of the brain. Lithium that gets forced out of the brain has to go somewhere, and if this were the case, it would probably end up in the urine, so you would see elevated levels of lithium in people who enter potato mode.
But maybe lithium causes obesity by forcing potassium out of the brain, and high levels of potassium cure obesity by supplementing potassium faster than the lithium can clear it. If something like this were the case, you might not see more lithium in people’s urine when they go on the potato diet.
Probably neither of these explanations are exactly correct — these are just examples to show that urine tests during the potato diet might be a good idea, but won’t be conclusive.
Something else about Potassium
But it’s also not like potassium and lithium are married. Potassium could still cause weight loss even if the lithium hypothesis is totally wrong. Potatoes are notorious for being high in potassium, so it’s reasonable to suspect that this might be the active ingredient.
That said, if it’s not lithium, why would potassium cause weight loss? We don’t know. Any ideas?
Don’t most theories predict weight loss on the potato diet?
Well, yes and no. Many theories do predict weight loss on the potato diet; but most theories don’t predict potato mode, this state where hunger disappears and you (occasionally) feel charged with incredible energy.
Finally, to anyone who thinks they knew it would work in advance…
Ok wise guy.
If you predicted (or could have predicted) that the potato diet would cause this kind of weight loss, or if medical / nutritional science could have predicted that this diet was going to be so effective in the short term, and so easy for so many people — then why haven’t doctors and nutritionists been recommending the potato diet to people alongside diet and exercise?
“I personally would not recommend it,” says Dr. Nadolsky. “It’s very restrictive. A vegan diet is very restrictive and a ketogenic diet is very restrictive, but a potato diet is one of the most restrictive diets you could ever do.” … the diet itself would be very hard to stick with for most people, says Dr. Nadolsky.
This type of extreme diet can pose serious health risks due to its severe limitations. “While there’s no doubt that potatoes — just like all vegetables — are supremely nutritious, eliminating almost all other food groups in totality is not only dangerous, but can really backfire,” says Jaclyn London, M.S., R.D., Nutrition Director at the Good Housekeeping Institute.
If you knew the potato diet would work, why did you not run this study many years ago? Why are there no clinical trials? Did you think people would not be excited to see this result?
Guess the NIH is too scared of the tater.
8. How to Potato Diet if you want to Potato Diet
We’re not currently accepting signups, but we know that some of you will want to try the potato diet for yourselves. So here is some current advice, from us and from some participants.
First, our advice:
When you start off, try eating mostly (> 95% of your calories) potatoes, with a little oil, and as much hot sauce and salt as you want. You can also have zero-calorie beverages like black coffee and tea. This seems really strict but many people find it to be much easier than they expected, so give this version a try first.
If you feel bad/weird and are like “I can no longer stand potatoes!”, try:
Eating a potato. Hunger feels different on this diet and you may not realize that you are hungry. Yes, really.
Drinking water. It’s really easy to get dehydrated on this diet, and again you can’t always tell.
Eating a different kind of potato. There are many varieties, try mixing it up. You will almost certainly want to eat more than one kind of potato.
Peeling your potatoes. Eating less peel / no peel seems to help some people with digestive and energy issues, especially after a few days on the diet.
Eating more salt. Potatoes are naturally low in sodium and you may not be getting enough.
Getting sunlight. Potatoes have no vitamin D, you may be craving that.
If none of these other things help, do a cheat meal and eat whatever you’re craving. (But maybe still avoid dairy?) If you find you keep taking cheat meals, go ahead and drop down to the 80%, 60%, or even a lower % potato diet. The 40% potato diet works just fine for some people.
If you still feel bad after trying these steps, stop the diet. If you are suffering then the diet isn’t working anyways, and you shouldn’t take risks with your health. Plus life is too short to do things that make you miserable.
If the diet is easy but you’re not losing weight (or otherwise not seeing effects), try doing 100% potato, no oil.
And here’s some advice from participants:
(33217580) I found that despite all the warnings, it was really easy to underprepare and end up with not enough food. The days where I either had done enough prep or just had time to go cook were definitely much simpler than the days where I would have been happy to just eat some boiled potatoes, but sadly the tupperware was empty, and I got really hungry, ate chips or fries, was a little lower on energy or moodier etc. If I’m going to continue (and I might, because it worked so well!), I’m going to aim for comically large proportions in food prep, because then I might actually have something close to enough.
(31664368) Advice: figure out a way to exit the diet gracefully. I have a robust belly, but significant GI issues I am still going through. Perhaps it was 1 thing I ate that set things on a bad track for several days. Trying oatmeal and crackers as easy non-potato food, but would love a playbook of how to get back to feeling solid after eating a burrito.
(14122662) If I were doing this again, I might also invest in a nice knife. I noticed that chopping the potatoes each day was effortful and a strain on my hand. Being able to slice through the potatoes more cleanly would have been a nice convenience.
(63187175) It requires a lot of preparation and staying ahead of your meals. Potatoes aren’t something you can just grab out of the cupboard and eat, there’s always some amount of cooking required and (at least in my limited experience) that cooking is either quite labor or time intensive (and usually both). If I do this again, my main takeaway lesson is that to be successful in sticking to it, I need to very deliberately over-prepare and always make way more than I want at a time. Just-in-time preparation is way too hard to follow. When I get home from a long day at work and discover that there are no potatoes already made, those were always the moments when I absolutely hated this diet. Even worse, I ran out of potatoes many times during these 3 weeks and had to take a trip to the store before I could even start cooking. Another area where I’d be more diligent if I try this again.
(02142044) How I’d do it again
– Ensure that my weighing scale is reliable
– Keep not using oil
– Stick to the diet strictly throughout
– Only eat potatoes boiled in their own water (mostly or only yellow?).
– Buy them in bio market if possible?
– Probably still eat sweet potatoes weekly for vit A?
– No exercises during this period.
– Do it in a period with less changes in my life overall (no medication, no changing location in between, no big relationship changes, etc)
– Keep filtering water throughout
– Change the way I track thing:
* Note how much kg of potatoes I eat each meals.
* Change “Mood” to “Lowest low”, “Highest high”, “Irritability”, “Fluctuation” and “Highest calm/plenitude”
* Keep track of “How tired am I of this diet?”
* Also note what is happening in my life to see other kinds of corelations.
– Supplement in B12 way more, salt my meals from the beginning
– No garlic. Cayenne pepper and tabasco are okay
(81125989) Advice to others trying the diet:
Feeling lazy? Trader Joe’s olive-oil Kettle-cooked potato chips for the win. Only three ingredients – potato, olive oil, and salt.
Choose cooking methods that are very low-prep-time, yet high-bulk. At first, I sliced potatoes before baking – this took over an hour each time and only made enough for one meal. Eventually, I realized I could just cut slits in whole potatoes, coat ’em in olive oil & salt, and dump ’em in the oven. Easy & makes enough for 2 days.
Variety is the spice of potato life. Get different kinds of potato, or you will get so intensely bored. (Also, get sweet potatoes for Vitamin A. Maybe placebo, but I noticed my evening low-light vision got worse, but improves the day after I eat sweet potato)
Schedule cheat days? I’ll have to wait to see your full analysis on the dose-response of the potato diet (weight loss vs days cheated)… but if the dose-response is good, then I recommend scheduling cheat days to stave off boredom. (Also, for social eating.) In particular, I ate red meats to get my B12. You can also eat liver or clams. Also potato has no Vitamin D, go get lots of sun or eat dairy/fatty fishes. (I don’t trust supplements; every time I’ve looked at a pre-registered RCT of a vitamin supplement, it’s either near-zero or somehow way less than just eating a whole food that’s known to be a source of it.)
– Buy lots of potatoes. Bake off or boil off five or ten pounds every couple days, then refrigerate to eat, mash, fry as wedges, roast as cakes, etc.
– Takiea baked potato that can be microwaved as needed, and or a small tupperware thing of mashed potato with some chilli/garlic/hot sauce in it when going places for long enough that being hungry will come up, but tables/utensils/microwaves etc will be available.
– Properly flavored mashed can be used as a dip for potato chips or something when going camping, etc.
– If with a group at a restaurant, order fries, or just have a beer. The mashed potato might be full of dairy fat.
– When eating non-potato snacks, make a note and carry on. Make sure they aren’t dairy.
– Make peace with breaking the diet for a meal every so often. It will happen sooner or later. Try not to, but eventually (group camping, or a nice restaurant, or something) it will be better to break the diet than not. Do so, and get back on potato immediately afterwards.
(21112694) While I only did about five whole days of the diet, I would highly recommend a 1-2 day transition off the diet. The day I ended, I went out for an event and had a large dinner which my digestive tract was not ready for. I typically have no issues with my GI tract, so I figured it wouldn’t be an issue given the shorter diet period. It could have just been a one-off random occurrence, but if you see this trend pop up more, it may be beneficial to suggest a slower transition off the diet, especially for those with GI issues like IBS (I don’t have any).
9. What’s Next
We’re very happy with this study, but there are some major limitations. Almost all of our participants were white, and most of them were Americans. We expect these results will generalize to other groups in other contexts, but frankly it’s not in the data.
The potato diet definitely causes weight loss, but a few major questions remain. Questions like, why do some people hit a wall immediately, and find the diet impossible after only a few days? Why do a few people suddenly hit a wall after about 3 weeks?
What’s up with cheat days? Does the 80% potato diet work for everyone? Can some people lose weight on the 40% potato diet? What about the 20% potato diet? The SMTM author who tried the potato diet didn’t lose any weight until they cut out all oil, at which point they started losing about a pound a day. So for some people it seems like the 100% potato diet is really necessary? Is that true? Why would that be?
Is the attrition rate really higher, and is the diet more difficult, for women / people with two X chromosomes? If so, why? What about trans people? If there’s a chromosomal effect, how does it interact with exogenous hormones?
All of these are questions that would be good to answer in future work.
Our current plan is to follow up with our participants in 6 months, 1 year, and 2 years (assuming it’s still interesting/relevant at that point). We’ll make posts with those results, and share the data publicly, as these followups happen, so look for the first followup post about six months from now.
We may also go back into these data and do more analyses, since there are almost certainly more things to find in the data we’ve already collected.
Also, expect a forthcoming post on reflections about doing this kind of shoestring internet science. Keep your eyes peeled.
We’re not currently taking signups, but if you want to try the potato diet for yourself, why not track your data using a structured spreadsheet, so all resulting data will be standardized. You’re welcome to download a copy of THIS FORM and follow the instructions, and you can send us an email with your copy of the form when you’re done. Just include the words “Potato Diet” in the email title so the emails are easy to sort and track.
If we can secure funding, our next study may be “potato camp”, a project where we send 20 or more overweight & obese volunteers to a summer camp and serve them nothing but potatoes for four weeks. This would allow us to replicate these results in a slightly more controlled fashion, collect things like urine and serum samples, and so on. And it would be a pretty good deal for participants — we’d make sure there’s wifi, so if you have a remote job, you can just drop by for four weeks and keep working as normal. If you’d be interested in attending potato camp, SIGN UP HERE. If you’d be interested in funding this project, contact us.
We might also run other studies, but we’re still figuring out what would be the best and most fun use of our time. Maybe we will run something on potassium. Or maybe our next study will be unrelated to obesity, it’s not the only interesting research topic in the world.
If you would like to be notified of future stupid studies like this one, SIGN UP HERE. You can also just subscribe to the blog itself by email (below), or follow us on twitter, if you want to keep up with our work in general.
And if you feel like reading this post has added a couple of dollars’ worth of value to your life, or if you have lost weight on the potato diet and you think it improves the quality of your life by more than one dollar a month, consider donating $1 a month on Patreon.
Thanks for going on this journey with us.
Sincerely, Your friendly neighborhood mad scientists, SLIME MOLD TIME MOLD
The TDS approach is pretty intuitive: if you want to study contaminants or residues that people are maybe exposed to through their food, one way to do that is to drive around to a bunch of actual grocery stores and supermarkets, buy the kinds of foods people actually buy and eat, prepare the foods like they’re actually prepared in people’s homes, and then test your samples for whatever contaminants or residues you’re concerned about.
A Total Diet Study (TDS) generally consists of selecting, collecting and analysing commonly consumed food purchased at retail level on the basis of food consumption data to represent a large portion of the typical diet, processing the food as for consumption, pooling the prepared food items into representative food groups, homogenizing the pooled samples, and analysing them for harmful and/or beneficial chemical substances (EFSA, 2011a). From a public health point of view, a TDS can be a valuable and cost effective complementary approach to food surveillance and monitoring programs to assess the presence of chemical substances in the population diet and to provide reliable data in order to perform risk assessments by estimating dietary exposure.
These papers include measurements of trace elements in various foods, and some of them include measurements for lithium. We didn’t find these papers while writing our first review of the levels of lithium in food and drink because these papers aren’t looking for lithium specifically — they’re looking at all sorts of different contaminants and minerals, and lithium just happens to sometimes make the cut.
But anyways, several of these papers do include measurements of lithium in various national food supplies, and they’re strange, because unlike every other source we’ve seen, which all routinely find some foods with more than 1 mg/kg lithium, they find less than 0.5 mg/kg lithium in every single food.
TDS with Li
The oldest TDS study we’ve seen that includes lithium is from 1999 in the United Kingdom, reporting on the UK 1994 Total Diet Study and comparing those results to data from previous UK Total Diet Studies. (The UK TDS has been “carried out on a continuous annual basis since 1966” but it seems like they only started including lithium in their analysis in the 1990s.) They report the mean concentrations of 30 elements (aluminium, antimony, arsenic, barium, bismuth, boron, cadmium, calcium, chromium, cobalt, copper, germanium, gold, iridium, iron, lead, lithium, manganese, mercury, molybdenum, nickel, palladium, platinum, rhodium, ruthenium, selenium, strontium, thallium, tin, and zinc) in 119 categories of foods, combined into 20 groups of similar foods for analysis.
The highest mean concentration of lithium they found in the food categories they examined was an average of 0.06 mg/kg (fresh weight) in fish. They estimated a total exposure of 0.016 mg lithium a day, and an upper limit of 0.029 mg a day, in the British diet at the time. This appears to be substantially less than the amount found in a 1991 sample, which gave an estimate of 0.040 mg lithium a day in the British diet. They explicitly indicate there is no data on lithium in foods (in their datasets) from before 1991.
France conducted a TDS in 2000, and a report all about it was published in 2005. They looked at levels of 18 elements (arsenic, lead, cadmium, aluminium, mercury, antimony, chrome, calcium, manganese, magnesium, nickel, copper, zinc, lithium, sodium, molybdenum, cobalt and selenium) in samples of 338 food items.
The highest mean concentration of lithium they found in the food categories they examined was an average of 0.123 mg/kg in shellfish (fresh matter) and 0.100 mg/L in drinking water. They estimated an average daily exposure of 0.028 mg for adults, with a 97.5th percentile daily exposure of 0.144 mg. They specifically mention, “drinking waters and soups are the vectors contributing most (respectively 25–41% and 14–15%) to the exposure of the populations; other vectors contribute less than 10% of the total food exposure.”
France did another TDS in 2006, with a report published in 2012. This time they looked at Li, Cr, Mn, Co, Ni, Cu, Zn, Se and Mo in 1319 samples of foods typically consumed by the French population.
Similar to the first French TDS, the highest mean concentration of lithium they found in the food categories they examined was an average of 0.066 mg/kg (fresh weight) in shellfish. But the highest individual measurements were found in two samples of sparkling water, with 0.612 mg/kg and 0.320 mg/kg.
New Zealand seems to run a Total Diet Study programme every 4–5 years since 1975, but we’ve only been able to find lithium measurements from this project in a paper from 2019, looking at data from the 2016 New Zealand Total Diet Study. Maybe, like some of the other TDS projects, they only started including lithium testing later on. Anyways, in this paper they looked at 10 elements (antimony, barium, beryllium, boron, bromine, lithium, nickel, strontium, thallium and uranium) in eight composite samples each of 132 food types.
This paper is a little strange, and unlike most of these papers, doesn’t give much detail. They summarize the main findings for lithium as, “the reported concentrations ranged from 0.0007 mg/kg in tap water to 0.54 mg/kg in mussels” and say that the mean overall intake of lithium in New Zealand adults is 0.020–0.029 mg/day.
The most recent TDS that looked at lithium seems to be this 2020 paper, which looks at food collected between October 2016 and February 2017 in the Emilia-Romagna Region in Italy. They looked at levels of fifteen trace elements (antimony, barium, beryllium, boron, cobalt, lithium, molybdenum, nickel, silver, strontium, tellurium, thallium, titanium, uranium, and vanadium) in 908 food and beverage samples from local markets, supermarkets, grocery stores, and community canteens.
The highest concentration of lithium they found in the food categories they examined was in fish and seafood (50th percentile 0.019 mg/kg, IQR 0.010–0.038 mg/kg), and legumes (50th percentile 0.015 mg/kg, IQR 0.006–0.035 mg/kg). They estimate a dietary lithium intake for the region of 0.018 mg/day (IQR 0.007–0.029 mg/day).
So overall, these papers report that lithium levels in foods and beverages never break 0.612 mg/kg, and almost universally keep below 0.1 mg/kg.
How About Those Numbers
We’re skeptical of these numbers for a couple of reasons.
The TDS papers say that all foods and beverages contain less than 1 mg/kg lithium, and that people’s lithium intake is well below 1 mg a day. But this is up against sources like the following, which all find much higher levels (not an exhaustive list):
Bertrand (1943), “found that the green parts of lettuce contained 7.9 [mg/kg] of lithium”
Borovik-Romanova (1965) “reported the Li concentration in many plants from the Soviet Union to range from 0.15 to 5 [mg/kg] in dry material”, in particular listing the levels (mg/kg) in tomato, 0.4; rye, 0.17; oats, 0.55; wheat, 0.85; and rice, 9.8.
Ammari et al. (2011), looked at lithium in plant leaves, including spinach, lettuce, etc. and found concentrations in leaves from 2 to 27 mg/kg DM.
Manfred Anke and his collaborators found more than 1 mg/kg in a wide variety of foods, in multiple studies across multipleyears, up to 7.3 mg/kg on average for eggs.
Schnauzer (2002) reviewed a number of other sources finding average intakes across several locations from 0.348 to 1.560 mg a day.
Five Polish sources from 1995 that a reader recently sent us reported finding (as examples) 6.2 mg/kg in chard, 18 mg/kg in dandelions, up to 470.8 mg/kg in pasture plants in the Low Beskids in Poland, up to 25.6 mg/kg in dairy cow skeletal muscle, and more than 40 mg/kg in cabbage under certain conditions. (These papers aren’t available online but we plan to review them soon.)
It seems like either the measurements from the TDS papers are right, and all foods contain less than 1 mg/kg lithium, or all the rest of the literature is right, and many plants and foods regularly contain more than 1 mg/kg lithium. The alternative, that both of them are right, would mean that the same foods consistently contain less than 1 mg/kg in France and New Zealand while containing more than 1 mg/kg in Germany and Brazil. This seems like the most far-fetched possibility.
There are three strikes against the TDS numbers. First, they’re strictly outnumbered. When five papers from four sources (two of those papers are from France) say one thing and the rest of the literature clearly says another, it’s not a sure thing, but the side with more evidence… well it has more evidence for it.
Second, the TDS studies have a divided focus. They’re not really interested in lithium at all; they’re interested in the local food supply, and lithium just happens to be one of between 9 and 30 different elements they’re testing for. In comparison, pretty much all the other papers are looking at lithium in particular. If we had to guess which kind of team is more likely to mess up this kind of analysis, the team interested in this one particular element, or the team that randomly included the element in the list of several elements they’re testing for, we know which we’d pick. It’s hard to imagine that every team looking for lithium chose the wrong analysis or screwed it up in the same way somehow. It’s easy to imagine that the TDS studies, which measured lithium incidentally, might get some part of the analysis wrong.
It’s kind of like clothing. Ready-made sizes will fit most elements, but if you have an unusual body type (really long arms, really thick neck, etc.) you may have to go to a tailor. And lithium has the most unusual body type of all the solid elements. It wouldn’t be at all surprising if off-the-rack clothes didn’t fit poor little lithium.
The third thing that’s strange is that there seem to be some internal contradictions within the studies. For example, in the first French TDS study, the lithium levels in water are much higher than lithium levels in things that are made out of water, which seems impossible. The mean lithium level in drinking water is 0.100 mg/kg, but the lithium levels in things that are mostly water are much lower: 0.038 mg/kg in soups, 0.006 mg/kg in coffee, 0.004 in non-alcoholic beverages, 0.003 in alcoholic beverages, and 0.002 in hot beverages. Soup is maybe a little different, but coffee and beverages are mostly water. How can there be fifty times more lithium in plain water than in hot beverages, which are (we assume) mostly water?
For that matter, how can drinking water be the category with the second-most lithium (after shellfish)? Water is the main ingredient in beverages, but it’s also a major ingredient of pretty much every food. Fruits, salads, milk, vegetables, etc. etc. all contain lots of water. Unless there’s some major, universal filtering going on, there should be more lithium in at least some foods than there is in water.
And that’s what you see if you look at the other elements in this first French paper — more in foods than in water. For example, the average level of manganese in drinking water in these data is 0.19 mg/kg, and the mean levels in beverages are all 0.30 mg/kg or higher; the mean level in soup is 0.97 mg/kg; the mean level in fruits is 2.05 mg/kg, much higher. Same for zinc. The mean level in drinking water is 0.05 mg/kg, which is the lowest mean level of zinc of any food category. Other elements, at least, tend to have higher concentrations in some foods than in water.
In the second French TDS study, the same thing happens. The highest concentration of lithium they found in any food was in water, 0.612 mg/kg. The mean for water this time around was only 0.035 mg/kg, but that’s still higher than the means for most beverages and the mean for almost every food.
(The other TDS papers don’t give mean lithium measurements for water, so we can’t do the same comparison with them.)
This doesn’t make much sense. Water is a major component of many foods and it would be shocking if lithium didn’t find its way from water into food (and more obviously into beer and tea). But all of the fruits and vegetables have less lithium than the water that would presumably be used to irrigate them.
There’s a rich literature of hydroponics experiments that shows that all sorts of plants accumulate lithium. When you grow them in a lithium solution under controlled conditions, or in soil spiked with lithium, the plants end up containing a higher concentration of lithium than the solution/soil they were grown in.
These spikes are much larger than the levels of lithium plants are normally exposed to in the environment, but they’re experimental evidence that lithium accumulates, even to enormous degrees. You should reliably expect to see more lithium in plants than in the water they’re grown with. There might be some plants that don’t accumulate, but water shouldn’t universally contain the highest amounts.
We didn’t really include these sources in our original review because that was a review of lithium in food, and these hydroponically-grown experimental plants aren’t in the actual food supply. But they’re pretty informative, so here’s a selection of the studies:
Magalhães et al. (1990) grew radish, lettuce and watercress in a hydroponic system, with solution containing lithium levels of 0.7, 6.8 and 13.6 mg/L. These are all somewhat high, but exposure to 0.7 mg/L in water isn’t totally unrealistic. Plants were collected thirty days after transplanting. At the lowest and most realistic level of exposure, 0.7 mg/L, lettuce contained 11 mg/kg lithium, radish bulbs contained 11 mg/kg, radish leaves contained 17 mg/kg, and watercress contained 37 mg/kg. At 6.8 mg/L in the solution all plants contained several hundred mg/kg, and at 13.6 mg/L, radish leaves and watercress contained over 1000 mg/kg.
Hawrylak-Nowak, Kalinowska, and Szymańska (2012) grew corn and sunflower plants in glass jars containing 0 (control), 5, 25, or 50 mg/L lithium in a nutrient solution. After 14 days, they harvested the shoots, and found that lithium accumulated in the shoots in a dose-dependent manner. Even in the control condition, where no lithium was added to the solution, sunflower shoots contained 0.9 mg/kg and corn shoots contained 4.11 mg/kg lithium. At 5 mg/L solution, sunflower contained 422.5 mg/kg and corn contained 72.9 mg/kg; at 25 mg/L solution, sunflower contained 432.0 mg/kg and corn contained 438.0 mg/kg; at 50 mg/L solution, sunflower contained 3,292.0 mg/kg and corn contained 695.0 mg/kg. These levels are unrealistically high, but the example is still illustrative.
Kalinowska, Hawrylak-Nowak, and Szymańska (2013) grew lettuce hydroponically in solution containing 0, 2.5, 20, 50 or 100 mg/L lithium. Lithium concentrations above 2.5 mg/L progressively fucked the plants up more and more, but there was clear accumulation of lithium in the lettuce. There was some concentration in the leaves in a solution of 2.5 mg/L (though they don’t give the numbers), and when the lettuce was grown in a 20 mg/L solution, there was around 1000 mg/kg in the leaves.
Antonkiewicz et al. (2017) is an unusual paper on corn being grown hydroponically in solutions containing various amounts of lithium. They find that corn is quite resistant to lithium in its water — it actually grows better when exposed to some lithium, and only shows a decline at concentrations around 64 mg/L. (“The concentration in solution ranging from 1 to 64 [mg/L] had a stimulating effect, whereas a depression in yielding occurred only at the concentrations of 128 and 256 [mg/L].”) But the plant also concentrates lithium — even when only exposed to 1 mg/L in its solution, the plant ends up with an average of about 11 mg/kg in dry material.
Robinson et al. (2018) observed significant concentration in the leaves of several species as part of a controlled experiment. They planted beetroot, lettuce, black mustard, perennial ryegrass, and sunflower in controlled environments with different levels of lithium exposures. “When Li was added to soil in the pot experiment,” they report, “there was significant plant uptake … with Li concentrations in the leaves of all plant species exceeding 1000 mg/kg (dry weight) at Ca(NO3)2-extractable concentrations of just 5 mg/kg Li in soil, representing a bioaccumulation coefficient of >20.” For sunflowers in particular, “the highest Li concentrations occurred in the bottom leaves of the plant, with the shoots, roots and flowers having lower concentrations.”
Again, these are unrealistic for the amount of lithium you might find in your food, but they’re clear support for the idea that plants consistently accumulate lithium relative to the conditions they’re grown in. It doesn’t make sense that we see water having the highest concentration in the TDS data.
So for all these reasons, we’re pretty sure that the TDS numbers are wrong and that the lithium-specific literature is right. Specialty research that looks for lithium in particular is more reliable in our opinion than sources that happen to look at lithium as one contaminant along with a dozen others.
But even so, you’d have to be terminally incurious to look at this and not wonder what was going on. Why do these five papers have measurements that don’t match the rest of the literature?
What’s Going on in the TDS
Since these papers disagree with every other source, and they all share the same Total Diet Study approach, it seems like there must be something wrong with that approach.
Sometimes this kind of mistake can come from problems with the equipment, dropping a decimal, or misreading units, like mistaking mg/kg for µg/kg.
But we have a hard time imagining that all of these different teams with (as far as we can tell?) no overlap in authors would be making exactly the same error of using the wrong units or moving a decimal place. It’s possible they all use the same slightly-misleading software or something; we have seen a few other papers that report lithium in one set of units, and every other element they test for in different units. But again, it would be weird for every single TDS study to screw this up in exactly the same way.
Samples of each food group … were homogenized and digested (0.5 g) in inert plastic pressure vessels with nitric acid (5 ml) using microwave heating (CEM MDS 2000 microwave digestion system). All elements except mercury, selenium and arsenic were analysed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) (Perkin Elmer Elan 6000).
The elementary analyses (about 18 000 results in all) were carried out by the Environmental Inorganic Contaminants and Mineral Unit of the AFSSA-LERQAP, which is the national reference laboratory. All the 998 individual food composite samples were homogenized and digested (about 0.6 g taken from each sample) in the quartz vessels with suprapure nitric acid (3 ml) using Multiwave closed microwave system (Anton-Paar, Courtaboeuf, France). The total content of all selected essential and non essential trace elements in the foods was determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) (VG PlasmaQuad ExCell-Thermo Electron, Coutaboeuf, France), a very powerful technique for quantitative multi-elemental analysis.
The National Reference Laboratory (NRL) for heavy metals was chosen to analyse 28 trace elements, and among them nine essential elements, Li, Cr, Mn, Co, Ni, Cu, Zn, Se and Mo, by inductively coupled plasma-mass spectrometry (ICP-MS) after microwave-assisted digestion.
Sample digestion was carried out using the Multiwave 3000 microwave digestion system (Anton-Paar, Courtaboeuf, France), equipped with a rotor for 8 type X sample vessels (80-mL quartz tubes, operating pressure 80 bar). Before use, quartz vessels were decontaminated in a bath of 10% HNO3 (67% v/v), then rinsed with ultra-pure water, and dried in an oven at 40 °C. Dietary samples of 0.2–0.6 g were weighed precisely in quartz digestion vessels and wet-oxidised with 3 mL of ultra-pure water and 3 mL of ultra-pure HNO3 (67% v/v) in a microwave digestion system. One randomly-selected vessel was filled with reagents only and taken through the entire procedure as a blank. The digestion program had been optimised previously (Noël, Leblanc, & Guérin, 2003). After cooling at room temperature, sample solutions were quantitatively transferred into 50-mL polyethylene flasks. One hundred microlitres of internal standard solution (1 mg L−1) were added, to obtain a final concentration of 2 μg L−1, and then the digested samples were made up with ultrapure water to the final volume before analysis by ICP-MS.
ICP-MS measurements were performed using a VG PlasmaQuad ExCell (Thermo, Courtaboeuf, France). The sample solutions were pumped by a peristaltic pump from tubes arranged on a CETAC ASX 500 Model 510 autosampler (CETAC, Omaha, NE).
We measured content of fifteen trace elements (antimony, barium, beryllium, boron, cobalt, lithium, molybdenum, nickel, silver, strontium, tellurium, thallium, titanium, uranium, and vanadium) in 908 food and beverage samples through inductively coupled plasma mass spectrometry.
Using a clean stainless-steel knife, we cut solid foods by collecting samples from six different points in the plate. Then, we homogenized the samples using a food blender equipped with a stainless-steel blade and we placed a portion of 0.5 g in quartz containers previously washed with MilliQ water (MilliQPlus, Millipore, MA, USA) and HNO3. We liquid-ashed the samples with 10 ml solution (5 ml HNO3 + 5 ml·H2O) in a microwave digestion system (Discover SP-D, CEM Corporation, NC, USA) and we finally stored them in plastic tubes, and diluted to 50 ml with deionized water before analysis. Using an inductively coupled plasma mass spectrometer (Agilent 7500ce, Agilent Technologies, CA, USA), we performed trace element determination.
So, all of these papers use the same analysis technique, ICP-MS. We don’t know the exact technique used by the team in New Zealand, but all the other teams used microwave digestion with nitric acid (HNO3). Three of them (the French and Italian TDS studies) used quartz vessels.
The fact that all these studies use similar analysis techniques makes it much more plausible that something about this technique is screwing up something about the lithium detection.
This also seems likely because most other papers, the ones that find more than 1 mg/kg lithium in food, don’t use ICP-MS. Here’s a small selection.
The most recent paper finding more than 1 mg/kg lithium in plant matter seems to have used inductively coupled plasma optical emission spectrometry (ICP-OES), a related but distinct technique. This is Robinson et al. (2018), which found that plants can contain “several hundred mg/kg Li” in leaves. Here’s their procedure:
Plant samples were washed in deionized water and dried at 60 °C until a constant weight was obtained. Subsequently, they were milled using a Cyclotech type 1093 cyclone grinder with an aluminium rotor. Plant material (0.5 g) was digested in 5 ml HNO3. The digests were diluted with Milli Q (Barnstead, EASYpure RF, 18.3 MΩ-cm) to a volume of 25 ml and filtered with a Whatman 52 filter paper (pore size 7 μm). … Pseudo-total element concentrations (henceforth referred to as “total”) were determined in the acid digests using ICP-OES (Varian 720 ES).
Ammari et al. (2011), looked at lithium in solids (plant leaves, including spinach, lettuce, etc.) and found concentrations in leaves from 2 to 27 mg/kg DM. They used this procedure:
Collected leaves were gently washed in distilled water, air-dried, and then oven-dried to a constant weight at *70°C. Dry leaves were finely ground in a Moulinex Mill (Moulinex, Paris, France) to pass through a 40-mesh sieve. As Li is known to be present in cell vacuoles in inorganic soluble form, Li was determined in filtrates of oven-dry ground leaf samples (5 g) suspended in 50 ml of deionized water for 1 h. This procedure was used in the current study because not all the lithium present in natural unprocessed foods is taken up by the human body (pers. comm. with nutritionists; Dr. Denice Moffat, USA). Lithium extracted with deionized water represents the soluble fraction that is directly taken up by the gastrointestinal tract and considered the most bio-available. … The concentration of Li in leaf samples was measured with a flame photometer.
Anke’s 2005 paper doesn’t give a ton of detail, but seems to have used atomic absorption spectroscopy (AAS) for lithium, and reports numbers up to 7.5 mg/kg in foods.
Thirty days after transplanting, the plants were harvested, shoots and roots separately, and their fresh weight determined. They were oven-dried at 700C for 72 hours, weighted, ground in a Wiley mill and analyzed for N, P, K, Ca, Mg, Fe and Li contents after digestion in H2SO4 and H202. N was determined by Nesslerization, P by an ammonium molybdate-amino naphthol sulfonic acid reduction method (Murphy & Riley 1962), K and Li by flame emission and Ca, Mg and Fe by atomic absorption (Sarruge & Haag 1974).
Drinkall et al. (1969), one of our oldest sources, found up to 148 mg/kg in pipe tobacco and used “the atomic absorption technique”. Specifically they say:
Methods for determination of lithium in foodstuffs have in the past been limited almost entirely to the use of the spectrograph and the flame photometer. In the present investigation, however, it was decided to apply the technique of atomic absorption for this purpose. The chief reason for this choice was the lack of occurrence of spectral interference occasioned by elements other than lithium, Indeed, the only elements which were thought likely to prove troublesome were calcium and strontium. Even these, however, were found not to interfere. The instrument used throughout this work was the Unicam SP90 Atomic Absorption Spectrophotometer, a propane-air flame being employed.
So this diverse set of methods all found levels of lithium above 1 mg/kg, while the “ICP-MS with microwave digestion in nitric acid (usually in quartz vessels)” technique seems to reliably find way less than 1 mg/kg. This is starting to look like it’s an issue with the analysis.
If this is the case, then if we can find other papers that use ICP-MS with microwave digestion in nitric acid, they should also show low levels of lithium, well below 1 mg/kg.
That’s exactly what we’ve found. Take a look at Saribal (2019). This paper used ICP-MS and looked at trace element concentrations in cow’s milk samples from supermarkets in Istanbul, Turkey. They found an average of 0.009 mg/L lithium in milk, way lower than the measurements for milk found in sources that don’t use ICP-MS.
Saribal, like the TDS studies, used ICP-MS to look for lithium alongside a huge number of other elements — 19 in fact. The full list was: lithium, beryllium, chromium, manganese, cobalt, nickel, copper, arsenic, selenium, strontium, molybdenum, cadmium, antimony, barium, lead, bismuth, mercury, thallium, and uranium. Like the TDS studies, they did digestion in nitric acid:
The quadrupole inductively coupled plasma mass spectrometer (ICP-MS) used in this work was Thermo Scientific X Series II (Thermo Fisher Scientific, Bremen, Germany).
One-milliliter portions of each milk samples were digested in 65% HNO3 and 2 mL 30% H2O2 (Merck, Poole, UK) on a heat block. The temperature was increased gradually, starting from 90 °C and increasing up to 180 °C. The mixture was cooled down and the contents were transferred to polypropyl- ene tubes with seal caps. Each digested sample was diluted to a final volume of 10 mL with double deionized water
Here’s another one. Kalisz et al. (2019) looked at “17 elements, including rare earth elements, in chilled and non-chilled cauliflower cultivars”. They used ICP-MS, they microwave digested with nitric acid, and they found lithium levels of less than 0.060 mg/kg. Here’s the method:
We investigated the content of Ag, Al, Ba, Co, Li, Sn, Sr, Ti, Sb, and all rare-earth elements. … Curds were cut into pieces and dried at 70 °C in a dryer with forced air circulation. Then, the plant material was ground into a fine and non-fibrous powder using a Pulverisette 14 ball mill (Fritsch GmbH, Germany) with a 0.5-mm sieve. Next, 0.5 g samples were placed in to 55 ml TFM vessels and were mineralized in 10 ml 65% super pure HNO3 (Merck no. 100443.2500) in a Mars 5 Xpress (CEM, USA) microwave digestion system. The following mineralization procedure was applied: 15 min. time needed to achieve a temperature of 200 °C and 20 minutes maintaining this temperature. After cooling, the samples were quantitatively transferred to 25 ml graduated flasks with redistilled water. Contents of mentioned elements were determined using a high-dispersion inductively coupled plasma optical emission spectrometer (ICP-OES; Prodigy Teledyne Leeman Labs, USA).
There are a couple complications, but they’re worth looking at. Seidel et al. (2020) used ICP-MS and found reasonable-seeming numbers in a bunch of beverages. But, as far as we can tell, they didn’t digest the beverages at all. They just say:
Li concentrations in our 160 samples were determined via inductively coupled plasma mass spectrometry (ICP-MS) as summarized in Table 1.
Here’s Table 1 in case you’re curious:
This seems like evidence that something about the digestion process might be to blame.
There’s also Voica, Roba, and Iordache (2020), a Romanian paper which used ICP-MS and found up to 3.8 mg/kg in sheep’s milk and up to 4.2 mg/kg in pumpkins. This is pretty surprising — it’s the first ICP-MS paper we’ve seen that finds more than 1 mg/kg lithium in a sample of food. They even use microwave digestion with nitric acid! So at first glance, this looks like a contradiction — but when we looked closer, their method did differ in some interesting ways.
The lithium concentrations were determined by inductively coupled plasma – mass spectrometry (ICP-MS).
Considering that samples have a very complex composition with large organic matter content, the total digestion of the matrix is mandatory to assure complete metal solubility. The studied samples were subjected to microwave assisted nitric acid digestion by using a closed iPrep vessel speed system MARS6 CEM One Touch. The digestion vessels were cleaned with 10 mL HNO3 using the microwave cleaning program and rinsed with deionized water. Approximately 0.3 g aliquots of the samples were weighed, followed by digestion in 10mL HNO3 60% at high pressure, temperature and in the presence of microwave irradiation. The vessel was closed tightly, placed on the rotor, and the digestion was carried out following the program presented in Table 1.
After complete digestion and cooling, the samples were filtered, transferred to 50 mL graduated polypropylene tubes and diluted to volume with deionized water.
A Perkin Elmer ELAN DRC-e instrument was used with a Meinhard nebulizer and a glass cyclonic spray chamber for pneumatic nebulization. The analysis was performed in the standard mode and using argon gas (purity ≥ 99.999%) for the plasma following the manufacturer’s recommendations.
The operating conditions were a nebulizer gas flow rate of 0.92 L/min; an auxiliary gas flow of 1.2 L/min; a plasma gas flow of 15 L/min; a lens voltage of 7.25 V; a radiofrequency power of 1100 W; a CeO/Ce ratio of 0.025; and a Ba++/Ba+ ratio of 0.020.
We don’t know exactly what the difference might be, but the fact that they mention that “considering that samples have a very complex composition with large organic matter content, the total digestion of the matrix is mandatory to assure complete metal solubility” suggests that they were aware of limitations of normal digestion methods that other teams may have been unaware of. And none of the other papers seem to have used pneumatic nebulization, so maybe that makes the difference and lets you squeeze all the lithium out of a pumpkin.
Another difference we notice is that while Voica, Roba, and Iordache do use ICP-MS and the same kind of digestion as the TDS studies, they don’t test for anything else — they’re just measuring lithium. So maybe the thing that torpedoes the ICP-MS measurements is something about testing for lots of elements at the same time — a trait shared by all the TDS studies, Saribal (2019), and Kalisz et al. (2019), but not by Seidel et al. (2020) (the beverages paper) and not by Voica, Roba, and Iordache (2020).
A final (we promise) paper that helps triangulate this problem is Nabrzyski & Gajewska (2002), which looked at lithium in food samples from Gdańsk, Poland. They found an average of only 0.07 mg/kg in milk products and of only 0.11 mg/kg in smoked fish. This is not quite as low as the TDS studies but it’s much lower than everything else. And weirdly, they didn’t use ICP-MS, they used AAS. But they did digest their foods in nitric acid. Here’s the method:
The representative samples were dry ashed in quartz crucibles and the ash was treated with suitable amounts of conc. HCl and a few drops of conc. HNO3. The obtained sample solution was then used for the determination of Sr, Li and Ca by the flame atomic absorption spectrometry (AAS) method. Ca and Li were determined using the air-acetylene flame and Sr with nitrous oxide-acetylene flame, according to the manufacturer’s recommendations.
So maybe this seems like more evidence that it’s something about the digestion process in particular, though this paper could also just be a weird outlier. It’s hard to tell without more tests.
Close Look at ICP-MS
We seem to have pretty clear evidence that ICP-MS, maybe especially in combination with microwave digestion / digestion with nitric acid, gives much lower numbers for lithium in food samples than every other analysis technique we’ve seen.
So we wanted to know if there was any other reason to suspect that ICP-MS might give bad readings for lithium in particular. We did find a few things of interest.
If you check out the Wikipedia page for ICP-MS, lithium is mentioned as being just on the threshold of what the ICP-MS can detect. This makes sense because lithium is unusual, much smaller than all other other metals. See for example: “The ICP-MS allows determination of elements with atomic mass ranges 7 to 250 (Li to U)” and “electrostatic plates can be used in addition to the magnet to increase the speed, and this, combined with multiple collectors, can allow a scan of every element from Lithium 6 to Uranium Oxide 256 in less than a quarter of a second.”
While ICP-MS is generally considered the gold standard for spectral analysis, like all methodologies, it has some limitations. Given that lithium is at the bottom of the range to begin with, it seems plausible to us that even small irregularities in the analysis might push it “off the end” of the range, disrupting detection. There’s more likely to be problems with lithium than with the other elements the TDS papers were analyzing.
We noticed that the 1999 UK TDS study had this to say about the upper limits of detection for ICP-MS: “The platinum group elements are notoriously difficult to analyse, as the concentrations, generally being close to the limits of detection, can be prone to some interferences in complex matrices when measured by ICP-MS.”
Now lithium is on the low end of the range, not the high range. But since the UK TDS study authors were concerned that elements “close to the limits of detection, can be prone to some interferences in complex matrices when measured by ICP-MS”, it seems like interference might be an issue. This shows that “fall of the end of the range” is a real concern with ICP-MS analysis. So ICP-MS may be the gold standard for spectral analysis, but it falls short of being the platinum standard.
Lithium may be determined in foods and biological samples with the same techniques employed for sodium and potassium. However, the much lower levels of lithium compared with these other alkali metals, mean that techniques such as flame photometry often do not show adequate sensitivity. Flame (standard addition procedure) or electrothermal atomic absorption spectrophotometry are the most widely used techniques after wet or dry ashing of the sample. Corrections may have to be made for background/matrix interferences. Inductively coupled plasma atomic emission spectrometry is not very sensitive for this very low-atomic-weight element.
As usual with Anke this is very cryptic, and inductively coupled plasma atomic emission spectrometry (ICP-AES) isn’t the same technique as ICP-MS. But even so, Anke’s comment does suggest that there might be some limitations on ICP methods when measuring lithium, that they might not be very sensitive.
We also found an article by environmental testing firm WETLAB which describes several problems you can run into doing lithium analysis, including that “[w]hen Li is in a matrix with a large number of heavier elements, it tends to be pushed around and selectively excluded due to its low mass. This provides challenges when using Mass Spectrometry.” They also indicate that “ICP-MS can be an excellent option for some clients, but some of the limitations for lithium analysis are that lithium is very light and can be excluded by heavier atoms, and analysis is typically limited to <0.2% dissolved solids, which means that it is not great for brines.” We’re not looking at brines, but this may also hold true for digested food samples. WETLAB indicates their preferred methodology is ICP-OES.
Maybe nobody knows what’s going on here! It’s looking more and more like this is just a question that’s sitting out on the limits of human knowledge. It’s a corner case — to know why some papers find high levels and other papers find really low levels, you might have to jointly be an expert on ICP-MS, lithium analysis, and chemical analysis in food. Manfred Anke is the only guy we’ve ever heard of who seemed like he might be all three, and he’s been dead for more than ten years. So maybe there’s no one alive who knows the answer. But that’s why we do science, right?
In any case, we’re very glad to know about this complexity early on in the process of planning our own survey, since we had also been planning to use ICP-MS! We had assumed that ICP-MS was the best technique and that it would certainly give us the most accurate numbers. But measurement is rarely that simple — we should have been more careful, and now we will be.
How do we figure out what’s going on here, and what technique we should use? We could go back and pore over the literature in even more detail. But that would take a long time, and would probably be inconclusive. Much better is to simply test a bunch of foods using different techniques, pit ICP-MS against techniques like AAS and flame photometry, and see if we can figure out what’s going on. So that’s what we’re gonna do.