Previous Philosophical Transactions:

• JP Callaghan on Lithium Pharmacokinetics
• Lithium in Scottish Drinking Water with Al Hatfield

The below is an email we received from M, a reader who tried a limited form of the potato diet that has been the recent focus of our research. Corroborating similar reports like Nicky Case’s experience with the half-tato diet, he readily lost weight despite the relatively low dose of potatoes.

The email has been lightly edited for clarity and to help preserve anonymity, but otherwise what appears below is a faithful reprinting of the original report as we received it. 

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Hello Slimes (Slime?),

I’m very excited to write to you. In some ways it is weird that you are the last to hear about my experience with the potato diet, since roughly everyone in my life has probably heard more potato-talk than they’d ever really want.

Starting in July, I ate “potatoes by default”, which is to say if I didn’t have anything better to eat, I’d eat potatoes. This meant that if I had plans for lunch or dinner, I would eat whatever it was I would’ve normally eaten ad libitum, and I tried actively to prevent the diet from materially interfering with my lifestyle (I drank alcohol socially as I normally would’ve, I participated in all the meals I normally would’ve participated in with friends, I tried arbitrary new dishes at restaurants, etc.). 

I started doing this because I was very intrigued by the reports of the changes to the psychological sensation of hunger in your study. I’ve always seen hunger as a psychologically weird thing. For example, I would often find myself physically extremely full to the point of discomfort, but would still want to eat more, especially if there was still food in front of me (often is not anywhere close to every day or every week, but frequently enough that this is an experience I feel pretty well-acquainted with). I would also tend to get super hungry around 5pm each day and couldn’t stop thinking about what I was going to have for dinner. I was also happy to lose some weight, but I value social life and food experiences pretty highly, and did not want any diet to interfere with these aspects of my life.

In practice, “potatoes by default” meant I was eating potatoes for roughly 1/3 of my meals, mostly for lunch when I was working from home during the week or on weekends, since I usually had dinner plans of some kind. My preferred preparation was to air-fry diced potatoes (unpeeled, though I’d typically use Yukon gold potatoes which have thin skins) tossed in some combination of {salt, soy sauce, pepper, dashi broth, herbs/spices, gochujang paste}, which I found to be both very tasty and time-efficient (~5 min of prep time and ~20 min in the air fryer). I would usually eat about 1 pounds of potatoes in a single sitting. I did experiment with a bunch of other preparations, and probably the most interesting thing I noticed here was that 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.

I tossed my diced potatoes in olive oil before air frying, and more generally used olive oil, duck fat and avocado oil to cook other potato preparations. I probably used 1-2 “glugs” of oil per 1-1.5lb potatoes across these preparations (“lightly greased”, call it). And of course in my non-potato meals, I consumed whatever oil – and other ingredients – restaurants would be using to cook their food. Given my diet was substantially made up of non-potato meals that I actively tried to keep “as before”, I think it is a safe bet that there wasn’t any particular type of food (diary, oil, red meat, etc.) I stopped consuming, or even materially reduced my consumption in, as a result of potatoes by default (beyond the generic ~1/3 reduction from swapping out a third of my meals to be mostly potato). FWIW, I tend to have low belief in hypotheses like “zero of X is special”; in general, I’d expect the difference in response between “zero” and “some” of any given input to be closer to continuous than discrete in the setting of a complex system like the one we’re thinking about.

The most succinct way to summarize the experience is probably with the below set of charts, which I had actually shared as part of a talk I gave at my fiancee’s company about potatoes and your work on obesity (I did say people around me have heard a lot about potatoes). The right chart is just a zoomed-in version of the left chart. The vertical red line is when I began the potato diet and the gray bars are when I was traveling / ate no potatoes. I plotted the results of your study in orange to compare; my version of the diet seems to be strictly less effective, but not by much I think. I wonder if the orange line (100% potato) would just hit the plateau faster, or if it would reach a different stabilized endpoint.

I think my main reaction to the data was that it was kind of insane? I was eating potatoes a third of the time and literally whatever else I wanted the rest of the time, and losing weight almost as quickly as the full potato diet. The gray bars (cumulatively more than a month) appear to make no dent in the overall trend, especially the first two bars when the weight loss was most rapid. Potatoes just seem unreasonably effective.

While charts are often worth many words, I think the qualitative commentary around the experience is probably just as interesting:

• Early on, maybe a two or three weeks in, for the first time in a really long time, I did not have the urge to finish off leftover food at dinner. That was a big “wow, what is going on” moment.
• The second gray travel bar was me traveling through Singapore and Bali. I’m a big fan of food, and was excited to try different hawker stands, etc. But I found my appetite was significantly diminished and I couldn’t try as much food as I wanted to. This was particularly striking since I was not eating potatoes at all in this period – there seems to be something more going on than just the “mechanical” effect of having potatoes in your belly (although I do believe high satiety per calorie is an important but incomplete part of the story; I think it’s unlikely that I’d consume much more than ~1000 calories/day if I was only eating potatoes, on the sole basis of how satiating they are).
• The third gray travel bar (the past week) was me spending time at my fiancee’s parents house for Thanksgiving. As a good future son-in-law, I basically just ate as much as they wanted to feed me, and of course it was a lot. So this was the first time during the course of the potato diet where I ate to the point of discomfort. Juxtaposed against the past couple of months, I was able to notice a very distinct difference in the sensation of full-ness here, which I think I can only describe as “physically full, but not spiritually full”. My stomach was mechanically full of food, but it was almost a completely different sensation of full-ness (and one that felt much “emptier”) than I’d have after eating a lot of potatoes.
• It’s been 4.5 months since starting potatoes by default, but I spent five weeks of those 4.5 months traveling / not eating potatoes. Conditional on not traveling, I think I ate potatoes for 1/3 on my meals (maybe more like 50% early on, and more like 20% more recently), but that means overall, I was really eating potatoes for only 25% of my meals on average in this period.
• After ~3 months, I went to my doctor to just make sure I was healthy, given the rapid and material weight loss I had been experiencing. He gave me a blood test for CBCD, CMP, a lipid panel, and HgbA1c, and apparently everything was fine (I have no idea what these tests are so just reporting them).
• I was extremely aggressive about cutting out eyes and sprouts in my potatoes when preparing them. I basically figured it was extremely costly to get sick of potatoes (or live in fear of eating a chunk of potato that tasted gross) if my goal was to eat potatoes long-term, and potatoes are very cheap from a $ perspective. So I’d strongly recommend anyone considering a long-term potato diet to do the same.
• I tended to keep skins on since I think they are good for fiber intake. But I find it harder to do this with thick-skinned potatoes like Russets. I have no issues at all with thin-skinned potatoes like Yukon gold.
• I was mostly not worried about nutrition, getting enough protein, etc., since the majority/supermajority of my meals were regular food.
• I play squash once or twice a week, and didn’t notice anything difference in my ability here. 
• I didn’t experience a feeling of increased energy as some others reported. 
• Given my experience, it seems like there is roughly no reason to go anywhere close to full potato. Just on priors, it seems kind of unlikely moving a relatively small portion of your diet to a single food would have any adverse health effects or other effects, and it seems you get pretty close to the benefits of full potato (though as noted above this depends a bit on whether the full potato diet gets you to the same plateau point faster, or gets you to a different plateau point). 
• I am planning on more or less just continuing to eat potatoes by default, possibly forever? There’s basically just no downside for me to do so, beyond the ~30 min of prep work I have to do to make potatoes (instead of say, ordering delivery as I normally would).

So, that’s the summary of the last 4.5 months of my life. My friends/coworkers have bought into potatoes to varying degrees, from simply no longer avoiding potatoes, to a friend participating in your KCl study. I hosted a Potato Con at my apartment a few weeks ago; we had 10+ unique potato dishes and a great turnout. I’m guessing as a fraction of my personality, potatoes will begin to fall off going forward, but as above, I expect as a fraction of my diet, they will continue to be a meaningful presence.

Thanks for all the super interesting research you guys have been doing on this. I read A Chemical Hunger at the start of July (two weeks before starting the potato diet), and found it incredibly compelling and well-researched. I don’t know if lithium is the thing, but the environmental contaminants hypothesis seems pretty hard to argue against. Keep up the great work, and let me know if there’s anything else I can tell you about my experience or otherwise to be helpful.

Cheers,
M