Background

Just over a year ago we launched the Potato Diet Riff Trial, the first of its kind.

The riff trial is a new type of study design. In most studies, all participants sign up for the same protocol, or for a small number of similar conditions. But in a riff trial, you start with a base protocol, and every participant follows their own variation. Everyone tests a different version of the original protocol, and you see what happens.

As the first test of this new design, we decided to riff on one of our previous studies: the potato diet. For many people, eating a diet of nothing but potatoes (or almost nothing but potatoes) causes quick, effortless weight loss, 10.6 lbs on average. It’s not a matter of white-knuckling through a boring diet — people eat as much (potato) as they want, and at the end of a month of spuds, they say things like, “I was quite surprised that I didn’t get tired of potatoes. I still love them, maybe even more so than usual?!”

Why the hell does this happen? Well, there are many theories. The hope was that running a riff trial would help get a sense of which theories are plausible, try to find some boundary conditions, or just more randomly explore the diet-space. We thought it might also help us figure out if there are factors that slow, stop, or perhaps even accelerate the rate of weight loss we saw on the full potato diet.

In the first two months after launching the riff trial, we heard back from ten riffs. Those results are described in the First Potato Riffs Report. Generally speaking, we learned that Potatoes + Dairy seems to work just fine, at least for some people, and we saw more evidence against the idea that the potato diet works because you are eating only one thing (people still lost weight eating more than one thing), or because the diet is very bland (it isn’t).

Between January 5th and March 18th, 2024, we heard back from an additional seventeen riffs. Those results are described in the Second Potato Riffs Report. Generally speaking, we learned that Potatoes + Dairy still seems to work just fine. Adding other vegetables may have slowed progress, and the protein results were mixed. However, the Potatoes + Skittles riff was an enormous success. 

Between March 18th and October 9th, 2024, we heard back from an additional eleven riffs. Those results are described in the Third Potato Riffs Report. Generally speaking, we saw continued support for Potatoes + Dairy.

The trial is closed, but since the last report, we’ve heard back from an additional two riffs, which we will report in a moment. This gives us a total of 40 riffs in this riff trial. Note that this is not the same as 40 participants, since some people reported multiple riffs, and a few riffs were pairs of participants.

Raw data are available on the OSF.

Last-Minute Entrants

Participant 87259648 did a Fried Potatoes riff, specifically, “mostly fried in a mix of coconut oil and tallow or lard” and continuing her “normal daily coffees with raw whole milk, heavy cream, honey and white sugar.”

Despite consuming only “around 30 percent potato on average”, she lost a small amount of weight and “found [the] diet to be easy and enjoyable, I never felt sick of potato although I did have a hard time getting myself to eat MORE potato each day.”

Participant 80826704 was formerly participant 41470698, but asked for a new number to do a new kind of riff. In Riff Trial Report Two, he had done Potatoes + Eggs as participant 41470698 and lost almost no weight. This time, he did a full potato diet and lost a lot of weight, more than 13 lbs: 

This definitely fits with our suspicion that eggs may be related to weight gain, and the observation that eggs often contain high concentrations of lithium.

Summary

Let’s recap all the riffs. Here’s a handy table:  

Mean weight change was 6.4 lbs lost, with the most gained being 5.2 lbs and the most lost being two people who both lost 19.8 lbs. One person gained weight, one person saw no change, one person reported no data, and the rest lost weight. One person also gained 6.3 lbs on “Whole Foods” + Chocolate, but this was not a potato diet (only about 10% of her diet was potatoes). 

Here are all the completed riffs, plotted by the amount of weight change and sorted into very rough riff categories: 

There are also a large number of people who signed up, but never reported closing their riff. We’re not going to analyze them at this point, but all signup data is available on the OSF if you want to take a look at the demographics. 

Things we Learned about the Potato Diet

The potato diet continues to be really robust. You can eat potatoes and ketchup, protein powder, or even skittles, and still lose more than 10 lbs in four weeks. 

The main thing we learned is that Potatoes + Dairy works almost as well as the normal potato diet. There were many variations, but looking at the 10 cases that did exclusively potatoes and dairy, the average weight lost on these riffs was 9.2 lbs. This is pretty comparable to the 10.6 lbs lost on the standard potato diet, suggesting that Potatoes + Dairy is almost as good as potatoes by themselves (though probably not better). 

We didn’t see much evidence that there might be a protocol more effective than the potato diet. This is sad, because it would have been really funny if Potatoes + Skittles turned out to be super effective. 

That said, three riffs did do unusually well, and it’s still possible that there is some super-potato-diet that causes more weight loss than potatoes on their own, or that’s better in some other way. 

There’s some evidence that meat, oil, vegetables, and especially eggs make the potato diet less effective. But with such a small sample, it’s hard to know for sure. This could be a productive direction for future research. You could organize it as an RCT, and compare a Just-Potato condition to a Potato + Other Thing condition. Or an individual could test this by first doing a potato diet with one of these extra ingredients for a few weeks, then removing the extra ingredient and doing a standard potato diet for a few weeks as comparison.

The strongest evidence is against eggs, because participant 41470698 / 80826704 did exactly that. First he did a Potatoes + Eggs riff and lost only 1.8 lbs. Then he did a standard potato diet and lost 13.2 lbs. That’s not proof positive, but it’s a pretty stark comparison. If that happens in general, it would be hard not to conclude that eggs stop potatoes from working their weight-loss wonders.  

Current Potato Recommendation

If you want to try the potato diet for weight loss, our current recommendation is this funnel:

1. Start by getting about 50% of your diet from potatoes and see how well that works.
2. If you want to be more aggressive, switch to Potatoes + Dairy. Try to get at least 95% of your diet each day from potatoes and dairy products, but don’t worry about small amounts of cheating.
3. If you want to be more aggressive, switch to the original potato diet. Try to get at least 95% of your diet each day from potatoes, but don’t worry about small amounts of cheating.
4. If you want to be more aggressive, switch to a strict potato diet. Try to get almost 100% of your calories each day from potatoes, allowing for a small amount of cooking oil or butter, salt, hot sauce, spices, and no-calorie foods like coffee.

If dairy doesn’t work for you for some reason (like you’re a vegan, or you just hate milk), consider replacing Step 2 with a different riff that showed good results, like Potatoes + Lentils or Potatoes + Skittles.

Remember to get vitamin A. Mixing in some sweet potatoes is a good idea for this reason.

Remember to get plenty of water. Thirst can feel different on the potato diet, you will need to drink more water than you expect.

Remember to eat! In potato mode, hunger signals often feel different. But if you don’t eat you will start to feel terrible, even if you don’t feel hungry. If anything, eating a good amount of potatoes each day may make you lose weight faster than you would skipping meals. 

If the potato diet makes you miserable, try the three steps above. If you try those three steps and you’re still miserable, stop the diet. 

Things we Learned about Doing Riff Trials

This is the first-ever riff trial. But it won’t be the last. So for the next time someone does one of these, here’s what we’ve learned about how to do them right.

#1: It Works

We hoped that riff trials would use the power of parallel search to quickly explore the boundary conditions of the base protocol, and discover what might make it work better or worse. 

This works. We had suspected that dairy might stop the potato effect, but we quickly learned that we were wrong. We saw that the potato effect is also sometimes robust to lots of other foods, like skittles. And we saw that other foods, like eggs and meat, seem like they might interfere with the weight-loss effect.

#2: You May Have to Encourage Diversity

That said, there was not as much diversity in the riffs as we might have hoped. 

Most people signed up for some version of Potatoes + Dairy. This was great because it provided a lot of evidence that Potatoes + Dairy works, and works pretty damn well. But it was not great for the riff trial’s ability to explore the greater space of possible riffs. 

In future riff trials, the organizers should think about what they can do to encourage people to sign up for different kinds of riffs. If you don’t, there’s a good chance you’ll find that most of your scouting parties went off in the same direction, and that’s not ideal if you want to really explore the landscape.

One way to do this would be to run a riff trial with multiple rounds. First, you have a small number of people sign up and complete their riffs. Then, you take some of the most interesting riffs from the first round and encourage people to sign up to riff off of those. You could even do three or four rounds. 

In fact, this is kind of what we did. Since we reported the results in waves, and had rolling signups, some people were definitely inspired to try things like Potatoes + Dairy or Potatoes + Lentils because of what they saw from completed riffs. But we could have done this even more explicitly, and that might be a good idea in the future.

#3: Riff Trials Harness Cultural Evolution

There’s no formal skincare riff trial. But it does kind of exist anyway. People get interested in skincare, and go look at other people’s routines. They copy the routines they like, but usually with some modifications. This is all it takes for skincare protocols to mutate, combine, and spread through the population, getting better and better over time.

The same is true of any protocol floating out there in the culture, including the potato diet itself. Even if we hadn’t run the riff trial, people would have experimented with potato diets for the next 10 or 20 years, trying new variations and learning new things about the diet-space. But this process would have been slow, and it would have been hard to tell what we were learning, because the results would have been spread out over time and space.

The fact that we planted our flag and ran this as a riff trial didn’t change the nature of this exploration. But making it one study, clearly marking out its existence, definitely sped things up, and helps make all the riffs easier to compare and interpret. 

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87259648 – Fried Potatoes

Riff 

Potatoes, mostly fried in a mix of coconut oil and tallow or lard. I will continue with my normal daily coffees with raw whole milk, heavy cream, honey and white sugar. Maybe occasional fruit on cheat days but mostly just potatoes, dairy, coconut oil, tallow, coffee and honey/sugar. 28 days. My reasoning for choosing this is that fried potatoes are delicious, i really don’t want to give up my coffee routine, or waste the raw milk that i get through a cow share, and anecdotally, coconut oil and stearic acid have both been reported to help with weight loss.

Report

So I didn’t lose a lot of weight, but I definitely lost somewhere between 3 – 6.5 lbs (hard to tell due to fluctuations in water weight) and an inch off my waist despite doing a pretty relaxed version of the diet. 

What I ended up doing was a diet of around 30 percent potato on average (even though I only ate potatoes for dinner and “grazed” on smallish things throughout the rest of the day, it was hard for me to get past around 30 percent potato calorie-wise). The rest of my diet was mostly dairy (raw milk, heavy cream, sour cream, butter, cheese and occasional ice cream), fruit, sugar (and sugary drinks), honey, chocolate and saturated fats (coconut oil and beef tallow).

I rarely boiled the potatoes so the potato portion of the diet was mainly peeled yellow or red potatoes pan-fried in a mixture of tallow and coconut oil, baked russet potatoes with the skins, or roasted red and yellow baby potatoes with the skins.

I occasionally supplemented extra potassium, as well as other supplements. Around day 5 I started drinking coconut water in order to get extra potassium.

I found this diet to be easy and enjoyable, I never felt sick of potato although I did have a hard time getting myself to eat MORE potato each day. The skins didn’t seem to bother me. Something about the diet definitely seemed to have an appetite lowering effect, although my appetite did fluctuate from day to day. I never intentionally cut calories or deprived myself of anything I really wanted. So even on the very low calorie days I ate as much as I felt like eating that day. (i am used to doing extended fasts so this is not super unusual for me, but I DO think that the extra potassium or something DID result in more days than usual where I didn’t feel like eating as much).

I didn’t exercise any more or less than I usually do.

My husband and another male family member did even less strict versions of the diet along with me (potatoes for dinner, whatever else they wanted the rest of the day) and they both seemed to lose more weight than I did, but they didn’t keep track of any data. I’m a 49 year old female, the other two men are 49 and 66. In the last couple years it has gotten much harder for me to lose weight, and I have been pretty fatigued in general. I didn’t notice any extra energy on this diet, but appetite did often seem suppressed.

I didn’t observe any noteworthy reduction in pulse or body temperature over the course of the diet. Three weeks after finishing the diet I have not been able to keep the weight off and am back up to 190.

I kept track of everything in the Cronometer app, so if you have any questions I can access some data that’s even more specific from there, let me know!

80826704 – Only Potatoes

Riff 

Formerly participant 41470698, who asked for a new number: “I would like to try the full potato diet at some point during 2024. Could you prepare a new Google Sheet for me for this purpose?”

Report

I completed the potato only version in August, but neglected to send you a report. Happy to report that I’ve completed it and filled the 4 week sheet.

In terms of feeling it was very similar to my riff experiment. In terms of results this has been completely different. One thing I am now throughly convinced about is the “ad libitum” part. I am hungry, I eat. It’s so simple it’s scandalous, but it’s been buried under years of well meant status quo advice.

From that point it simply matters which food types I eat. Even if the lithium hypothesis turns out wrong, this part I am thoroughly convinced about now.

Difficulty

In a way this was easier than potatoes + eggs. One reason I remember for this was the forced pre-planning. Because I knew I was going to eat only potatoes I generally tried to peel way more potatoes than I was hungry for. Because of this, for the next meal I would have potatoes already lying around. I could then eat those as-is, or more tasty, (re-)baking them in a frying pan.

Somehow I had less inclination to cheat.

I’ve also gone to McDonalds like 6 times, ordering only fries without sauce. And a lot of fries from a Snackbar (https://nl.wikipedia.org/wiki/Snackbar). It’s super convenient when going by train to just order a big portion of fries without sauce.

Fun stuff

Potatoes are fucking delicious by the way. I’ve taken to eating them without sauce, because now it just feels like potatoes with sauce taste like sauce. And then I’m missing the potato flavor. Maillard reaction for the win.

With a group of friends I did a “potato tasting”. I bought 8 breeds of potatoes and cooked them with the oven or boiled. So we tasted 16 different kinds. People were truly surprised by the amount of variation.

My surprise was mostly about how difficult the different breeds were to peel. Some potatoes are truly monsters.