Results of the 50%-potato diet experiment

Introduction: The bloggers at “Slime Mold Time Mold” recently launched a crowdsourced experiment to test a proposed weight-loss program. This initiative was inspired by a prior experiment, also crowdsourced, which revealed that a diet consisting mostly of potatoes could lead to substantial weight loss. In this earlier study, participants were encouraged to eat nothing but potatoes. However, many participants exhibited significant weight loss despite the fact that they often “cheated” by consuming other foods. Consequently, the bloggers came up with the “half-tato” diet hypothesis. This posits that even if only half of your calories come from potatoes, you can still lose weight.

I didn’t participate in the earlier “full potato” experiment, but I did sign up for the “half-tato” diet. My body mass index (BMI) is around 31, so I was cautiously hopeful that I could lose weight via a fairly simple change to my eating habits. Unfortunately, my results were disappointing.

Results: The graph below shows a 28-day baseline of daily weights, followed by 28 days on the 50%-potato diet. The solid black line is a 5-day moving average. The green line is a linear regression line. The graph shows an unexpected weight gain during the pre-diet baseline, followed by a significant drop during the early stages of the diet. Afterward, my weight crept back up to baseline levels.

Discussion: The diet itself was fairly easy to maintain. I would typically eat a big breakfast consisting of potatoes (usually russet) topped with Earth Balance margarine, Tofutti vegan sour cream, and seasoned salt. (I’m a vegan for ethical reasons.) Lunch would be similar, and dinner was a normal vegan meal, though sometimes accompanied by a side of potatoes. I was surprised that I never really got tired of potatoes during the four-week trial. I usually cooked the potatoes whole, either in an Instant Pot (pressure cooker) or a microwave oven. Sometimes I refrigerated the potatoes before eating them the next day. Sometimes I would eat them freshly cooked. I should note that I didn’t keep rigorous track of my caloric intake, so it’s possible that my potato calories were lower than I thought.

I did experience some mild indigestion on occasion, particularly after dinner. I also found that my cardio workouts (running or riding a stationary bike) became significantly more difficult, at least for the first few weeks of the diet. Also, I developed an unexpected craving for pickled things. I ate a lot of lacto-fermented pickles and sauerkraut during the diet. A lack of salt can’t explain this craving because I would typically season my potatoes with a significant amount of flavored salt.

Before I embarked on the half-tato diet experiment, I had been following the “Shangri-La” diet as developed by the late psychologist Seth Roberts. A book-length treatment of the diet is available here. Roberts also wrote a shorter summary (scroll down to page 7 of that PDF). I started the diet in October 2009 and have been following it ever since. This diet worked well for me at first, and I easily lost a significant amount of weight without feeling hungry. However, over the years, the diet has become less effective, and much of the weight came back. I was hoping that the “half-tato” diet would jump-start my weight loss. Since that didn’t happen, I will now return to my earlier eating habits, which I find convenient for reasons unrelated to weight loss. If I had more time, I would write an up-to-date summary of my experience with the Shangri-La diet. However, I do have an earlier summary that I had posted on a now-defunct personal website.

Other thoughts: The half-tato diet experiment was worthwhile, despite the fact that I didn’t lose any weight. I would be interested in participating in future studies (and I would particularly love to see a community study of the Shangri-La diet). I do have two suggestions based on my experience with the half-tato study.

I think these sorts of crowdsourced studies would be more fun if there were a way that participants could communicate with each other. Perhaps there could be a private, anonymous message board. I would have enjoyed hearing about people’s experiences, recipes, suggestions, life hacks, etc. Plus, it’s also just interesting to meet the types of intellectually-curious people who enjoy doing personal science experiments on themselves. Some people did choose to post updates on Twitter, but that platform is controversial and is probably sub-optimal for this purpose.

Another suggestion would be to include specific, organized guidelines for participants. Are sweet potatoes (or yams) considered “potatoes” for the purposes of the study? How many potatoes should one eat (roughly) to consume 1,250 calories? Should people peel their potatoes? Why might ketchup and other tomato-based foods interfere with weight loss? What’s the deal with dairy products? Some or all of these questions may have been answered in various locations on the blog (or were answerable from Google searches), but it would be useful to have a concise guide that participants could reference. .

I’m happy to communicate with anyone who might be interested. I can be reached at — Alex C.