Slime Mold Time Mold (SMTM) has just published the results of their studies on the potato diet. The idea is to eat nothing but potatoes for four weeks, and report how it went.

You can read SMTM's reasoning here, the basic idea is that they've observed some annectdotal data point of some people losing substantive weight while eating nothing but potatoes and want to reproduce the result.

Natália Coelho Mendonça has written in a very detailed and well-written article why it was probably not lithium, SMTM's leading hypothesis of why obesity is so prevalent.

As SMTM's potato diet is not directly linked with lithium, some readers might think that even if SMTM was wrong on that one, the potato diet could be interesting to try.

Having done the diet, I thought I could give a subjective data point into all this. I wanted to be pseudo-anonymous, but this post has been nagging at me ever since finishing the diet.

This post will not be as sourced as Natália's article, I do not intend to explain the mechanism or absence thereof of the potato diet. I am not knowledgeable in nutrition or biology to really have any insights into the mechanisms of this.

This article will serve both as a report of how it went down for me, a postmortem of mistakes I made, and a general impression of the SMTM methodology that results from this.

While I am glad I tried the potato diet, and it gave me great insights into what can affect my energy and mood levels, I feel that my following of it was dangerous in a way SMTM did not account for. I am also finding their methodology has been very poor, and their recent article is loose in the way it draws its conclusions.

There are some things I either completely blundered and that were my fault, or that I calculated the risks of and decided they were worth the gamble. For instance, I asked SMTM if my bipolar anorexia would muddle the data, to which they said that they advise against bipolars taking the diet. Seeing as I am quite atypical in my bipolarity (my manias are never a problem for me, I actually look for ways to trigger them), I decided it was worth a shot.

So I am not trying to hold SMTM responsible for what happened or what might have happened. I am trying to

  • warn other users here who might be tempted to follow the diet of precautions they might want to take into considerations
  • narrate my experience as a whole in case there is something interesting for other people.

A quick TLDR of the (long, sorry) following post:

  • Personal experience:
    • First started the diet eating self-made, oilless fries and chips/crisps, as well as potato soup. Then, as there were no effects, switched to whole boiled potatoes on their recommendations
    • Got some bruises/maybe oedema and general dizziness after stopping the diet, which I think is mild refeeding syndrome
    • Lost 8 pounds in 4 weeks, regained them completely 2 weeks after the diet
    • I was in a quite low energy state for months, I am now having bipolar swings and low sleep for two weeks (as I knew about being bipolar, those were risks I knew of and somewhat expected)
    • I still do not understand why eating the potatoes whole and boiled had an effect when nothing else worked. Especially seeing that I seem to be the only one. Solanine poisoning? Placebo effect? Weird timing?
  • SMTM's methodology:
    • The design of the study was very weird, sometimes it would be about trying to reproduce the potato diet, and other time to search for a diet that would work.
    • The features of the change they were looking for were themselves not fixed in time
    • I do not think SMTM took enough precautions in safety communication
    • SMTM seemed focused in confirming their hypothesis rather than challenging it
    • Weird felt sense that might just come from my shift in perspective as a whole
  • Lessons learned:
    • Start taking daily pictures of myself as a way to log changes. Diversify what kind of data to track.
    • If you want to track the effect of an intervention, ensures your life will be stable enough during to avoid confounders.
    • If something seems potentially dangerous, open a manifold market asking "Will I in retrospect think X was hazardous for me to try?"
    • Do not go into something with such a high investment as one month before you either have a very thorough understanding of it, or that you have already experimented with smaller variants of the experiment
    • Alimentation seems to have high leverage over my mood and experimenting more with this could be a solution to trigger my hypomania more reliably, and just to manage my mood in general.
    • This might also reflect more of this type of experiment within the rationalist community as a whole, and I still have to ponder more about this. - Conclusion:
    • If you want to try the potato diet, please don't be reckless. Low risks high rewards only apply if the risks are low, and I don't think there's been enough evidence of this for doing the diet a full month.
    • Please don't take up on SMTM for doing a study on the Onion Diet unless you can have way more responsibility in your approach.

Personal experience

This section is given for context, feel free to skip it.

For full transparency, I feel that it is important to give my datasheet and emails I've sent them. I think one of the answer they've sent back as a mail is crucial in how I felt and that I should include it as well. As it is anonymous, I believe this is fine, and I believe the inclusion of my data should not be problematic now that the study is over.

If you feel a link or text I give is not ethical/correct for me to put here, please do signal it and I will remove it posthaste

I am number 02142044, here is my data sheet . I also reported some of my experience on a manifold market

Diet overview

The gist of my diet:

  • Did not use oil at all during the whole month.
  • Used potatoes from the mall
  • Started with oil-less self-made chips (crisp), moved on to whole boiled potatoes at their suggestion
  • Some occasional breaks during the weekend.

Reasons for the diet

My main motivations for taking the diet were threefold:

  • I want to lose weight for aesthetic and/or social reasons. Because I have had induced anorexia two times before, during which I lost 10 kg in a month, I was looking for a way that would not trigger it and that would be safe for me. It seemed to me that this diet could fit the bill.
  • As mentioned before, my manias have never been problematic for me. I am looking for a way to be more frequently in a hypomanic state, as it is very pleasant and productive.
  • Mostly, I am very much into applied transhumanism and looking for new ways to do science and data-collection, so this idea seemed very appealing to me. I estimated the risks were not high based on the accounts they had and other information I gleaned.

So I was excited to explore this diet.

Before the diet

Before starting the diet, I was in a quite low point in mood-space for months (might have been depression). I was a bit apprehensive of what dangers the diet could have and was talking frequently to my brother about this.

Start of the diet

As I started my diet, I was mostly eating the potatoes in chips/crisps or soup, and was seeing no effects at all. It put me in an uncomfortable state of constant hunger, where I would always want to eat. I tried several variations to remediate that: eating them cold, adding salt, stopping seasonings...

I was starting to get a bit desperate from this, and I was wondering if I should just cut the diet altogether as I saw no changes at all. One of the main reasons I was unsure about quitting is that I thought they might not include my data if I did not continue until the end, and I was relatively certain, seeing how much my experience differed from the others, that it would not see any improvements at all.

12 days in, I thought I might quit and sent them this email:


I am on the 11th day of the potato study (my spreadsheet: ), and am not feeling much different, either in terms of energy, mood or weight. Would it give you more interesting data if I continued the study?

I do not really mind, the biggest problem for me is that I do not know what you would recommend, like if I should only eat them whole and not sliced&broiled, or unseasoned. If I had to eat them only boiled and nothing else without any seasoning I might start to find it untenable, though I can try.

Otherwise, I might stop the diet, as it leaves me quite hungry and does not seem to have any benefits.

Thanks a lot!

To which they answered

Thanks for checking in. If you're feeling poorly you should end the diet and finish the study, we don't want anyone to take risks with their health and comfort. But if you're feeling ok here are a few ideas of things you could try that might make a difference:

  • Start peeling the potatoes, eating them without most or all of the peel. Some people seem to find this makes a difference.
  • Try cutting out all oil from the diet. The SMTM author who tried the diet didn't start losing weight until trying the diet without oil.
  • Eat more whole potatoes. Someone mentioned that cooking potatoes in smaller pieces might cause some of the potassium to leave the potato and end up in the cooking water or whatever, so if potassium is part of why the diet works, that could be a problem. You could also do sliced potatoes in a soup and just drink the water they were cooked in.
  • Try avoiding tomatoes. We see on your sheet that you sometimes have had tomato sauce. Other participants have mentioned that they seem to stop losing weight when they use ketchup, and given that we've recently found sources suggesting that tomatoes may be lithium concentrators, they might be worth avoiding.
  • We recommend that you keep eating your potatoes seasoned, that seems to work for almost everyone, and it's more enjoyable. A lot of people swear by Frank's sauce. When the SMTM author who tried this was on the strictest form of the diet, they were just having potatoes, Frank's sauce, salt, and black coffee, and that worked surprisingly well for being so restrictive. Salt might even be important if the mechanism is something like a potassium/sodium balance thing.

Let us know if you have any questions!

(I should note that on day 7, I started working on my (non-physical) projects a lot more, but I did not notice it until the diet was almost done. Before the diet fluctuation in my concentration and procrastination was very high, so it did not seem unusual, and it did not fit any cases of the data sheet - I did not feel any more energetic. This productivity is still ongoing a month later, and it is very rare for me to maintain such a high streak. However, I am skeptical this is related to the potato diet, as I was also ongoing a lot of relationship/life changes.)

Switching midway

Following their recommendation, I stopped broiling the potatoes and only started eating them boiled whole from day 12 forward. Weirdly enough, this seems to be the moment a change started to kick in, I was getting less and less tired of the diet, and also eating way less. The hunger sensation started to dissipate, and this was a pivotal moment in the diet for me.

On day 17, hypomania kicked in, and lasted for about 4 days, my mood kept swinging after that.

I do not feel comfortable describing this fully, however after switching to boiled potatoes, there were signs of body dysfunctions. Because of complicated reasons, this did not alert me while it should have. This was my fault and caused by a faulty assumption of mine.

I do not yet know how to make sense of this, except to have better tracking in general. The signs resorbed swiftly after stopping the diet.

After the diet

You can read the full report I sent SMTM here. This was written just after I was done with the diet.

Two days after stopping the diet, I noticed a bruise and maybe oedema on my forearm, about 10 cm wide. I did not sadly take a picture of it. I realize now that this was likely mild refeeding syndrome which is what happens when the body has a sudden influx of calories. I also became significantly tired for a few days.

To the best of my knowledge, SMTM does not say anything about how to ease back out of your diet, just "you can eat whatever you like". I believe, now that I have read more about it, that this is a mistake. If by any mean you are doing the potato diet, please do consider ways to ease back out of it.

Something very interesting that was happening to me that might be related is that I noticed my hunger was offset. In the sense that I would start eating, and my body would just feel full, but the sensation of wanting to eat was still there. I thought it was a sign that the diet worked and that my "wanting to eat" sensation would adjust, but now that it didn't, and my hunger has rekindled even greater, I am wondering if it was a way to regulate against the refeeding mentioned above.

2 weeks later, I have now fully regained the weight I lost and feel quite hungry all the time. I am noticeably more fluctuating in my mood, with 2-3 mood swings per day and sleeping ~6 hours a day. I am now still working a lot more, with noticeably less procrastination/watching youtube/etc.

Overall the outcome is positive for me, I highly prefer frequent mood shifts to constant low. I cannot however say that

  • the outcome was positive in expectation
  • that it was related fully or partly to the potato diet (my prior is that it is a loose link).

Making sense of all this

I still do not understand why eating the potatoes whole and boiled had an effect when nothing else worked. Especially seeing that I seem to be the only one. Solanine poisoning? Placebo effect? Weird timing? The heat wave?
The fact I fully regained my weight while feeling insatiable makes me lean toward "it was just malnutrition", with solanine poisoning lingering in my mind.

The bipolarity symptoms are still present. This could be a very weak update for lithium, though I do not think they are discriminant enough to not be explained by "just malnutrition+a lot of life changes".

SMTM's methodology

Preregistration and conflation of the experiments

One of my biggest gripe with this experiment is that it was very unclear what they were going for. A lot of the general vibe, which I can appreciate, is that they were trying to explore the space of diet: "We see that some persons are very successful in a diet made only of potatoes, is there something to it, or is it just anecdotal myths? Let's explore around eating only potatoes."
This could explain why they told me to change the way I was doing the diet, while in other cases it could have be seen as data manipulation.

But those features clash with the design of the study: It only makes sense to go for a month if you have a well-prepared plan in mind. The affirmed purpose of the study is also to reproduce a result, and their article presents it as such.

I think the general intent of "let's explore around this" is very interesting, but I regret there has not been any kind of preregistrations and the guidelines were so loose. Another point which perplexed me is that they gave feedback on how other participants were doing, but not opening the data to everyone. It gives an air of studying it together, while all the insights are centralized by SMTM.

I believe the best way to have gone about this would have been to recognize the features of the anecdotal successes around the potato diet and to search for variations of the potato diet that would give those features.

In particular, that it seems to occur very rapidly (less than 5 days), and to open a Scott Alexander style of study: Preregister what you are going to try and for how long (probably just a week), and report on your own trial. Then only try to reproduce when there is already a well-defined plan you want to ask your participants to stick to.


This is related to my latter point. In the answer SMTM sent me, they say

  • Try avoiding tomatoes. We see on your sheet that you sometimes have had tomato sauce. Other participants have mentioned that they seem to stop losing weight when they use ketchup, and given that we've recently found sources suggesting that tomatoes may be lithium concentrators, they might be worth avoiding.

This was I believe the first moment I started being uneasy about this. When asking for advice, it had been 4-5 days since I had tomatoes, and was still not seeing any changes. I was also not seeing any changes for the beginning of the diet. This, I believe, was atypical of the diet's effect they were looking for, which usually kicks in less than 5 days and is fairly robust to eating something else.

I am not saying they were necessarily wrong in this. It might be that the "kicks in less than 5 days" data points were actually outliers. I am saying that the effect they were trying to find seems to itself have changed over time.


While SMTM does say to consult a doctor, I believe there are several points they have not been cautious enough in the impact of:

  • A month is a lot. Why start with a month? Is there any basis for this? This is especially weird when their data sheet goes up to 9 weeks (!!) and they say "We think you probably should stop here (or at least email us to let us know how it's going). But if you really want to keep going, just keep adding more columns!" which seems a mild way to put it at best.
  • Not warning about refeeding syndrome and ways to ease back from the diet as mentioned earlier.
  • In general, very little data about what kind of impact such a drastic diet could have, what to expect, and what to look for in terms of problems.

EDIT: I'm not saying they should have made sure it was 100% completely safe. I am saying that the same way they instructed to supplement in vit A and B12, they should have quickly checked for ways to secure this experiment, and communicated on this degree of safety and certainty in it.

For instance, saying clearly (and in neon signs) "We did not do any research into what kind of impact this can have and there may be very non-obvious negative impacts you will not notice and be aware of"


I think a general issue is that their experiments seems to try to confirm their leading hypotheses rather than refute it.

As an example, here are two things that puzzled me:

  • SMTM seems to take prevalence of hypomania and agitation in participants as a strong update toward lithium clearing. I believed that too, as discussed in the next section. However, this now seems wrong to me and I think they could have discounted it a lot more at that point:

    • Hypomania and agitation is a common answer, especially during a physically stressing time. For instance, sleep deprivation is quite known to cause hypomania or full-on mania.
    • For another anecdotal example that is the closest I could find to the potato diet, Mr Beast also experienced hypomania when fasting for two weeks six days after start
  • SMTM does not seem to really consider alternative diets. They do mention mono-diets, and other type of diets, but since they were working from anecdotal data point in the beginning, it seems weird to me they did not contrast it with others (I mean wikipedia gives George Sitwell who ate only chicken and Howard Hughes who ate only canned soup as examples. I do not understand why they did not contrast the anecdotal successes of the potato diet with them and try to see if there was something very specific about potatoes from the start)

Foregoing the conclusion

Related to the previous point, a lot of the effects Slime Mold Time Mold discusses in their more recent article seem weird to me, in that I am not sure most of them distinguishes with a potato diet as opposed to simple malnutrition. Weight loss, hypomania, cholesterol, libido, ...

One way this could resolve is if it actually was safe to follow through. Then the effects themselves would not matter as much: Reproducing malnutrition's benefits without its drawbacks would be awesome enough.

However, I don't think that SMTM has done enough to show that it was safe. There is little about potential solanine poisoning and ways to avoid it (especially since they said to eat the peels at the beginning), about what to track before stopping, etc


This is going more in the "diffuse feeling" part, i.e. issues that may not be issues and depends on your prior in how you interpret them.

SMTM quotes me as saying:

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. seems to indicate that potassium and sodium can help with clearing lithium. That is also why I started salting more.

(I no longer support this for reasons mentioned above)

The thing is they already had this as a potential hypothesis, quoting from their mail

Yes, this is our suspicion as well! This might also explain why some people get feelings of dread/despair instead of hypomania.

I am confused as to why they quote me. It could be a simple explanation like they want to give credit, or that they want to emulate discussions and problem-solving. It could be that since the it's probably not lithium article released, I no longer support this hypothesis, and so seeing it here is strange for me.

One thing however that I am wary it could be read as - whether or not that is their reasons for doing so - is an update toward lithium, i.e. "we are not the only one to think this!"
So just in case, and because I am still feeling uneasy about all this, please disregard my comment as an update, the fact a random person who undertook the study think/thought that lithium contamination is the source of obesity should not be an update in itself, only the link I gave.


This last diffuse feeling point is not about SMTM itself, but about comments I've read generally. I still add it as something to be wary about if you are doing the potato diet.

Something that rubbed me the wrong way is the fact that some people would congratulate me for "sticking through it", and others would more generally say "congratulation to everyone who made it through".

It might be that one problem I see is that this directly contradicts the safety precautions one should take about quitting if feeling sick or unwell, and added irony in that the potato diet was supposed to be easy in the first place.

Lessons learned

Data tracking

In general, I am not tracking data regularly, and I should fix this.

But on the study itself, one of my shortcoming in all this is that I relied on SMTM's template while I should have made my own rows for tracking. I should have asked myself general categories to put in, especially anything I was worried about (like agitation or physical weakness)
Also, I should have diversified what I tracked, track variables I do not know the impact of yet, or that are holistic in nature. Taking photos of myself regularly is a good way to notice any progressive change for instance, and to have a global view of what is happening.

Stable baseline

Relatedly, I notice a lot of things are changing in my life at the same time. I should wait for all of it to calm down before experimenting more if I want to have data, as an unstable baseline makes the data confused.


Another failure of mine is that, while I did see the diet was potentially dangerous, I did not set enough fallbacks for me to track how I was doing. In particular, I knew that change could be progressive and that the jump from "this feels weird" to "I should quit" is not automatic.

One way I see how I could have solved this is to open a manifold market asking "Will I in retrospect think that my doing X was hazardous?" and update it frequently. Then, if the probability gets too close to YES, stop immediately and resolve it later.

I did open a market, but it was asking the wrong question with the wrong incentives, as it was about how long I was going for.

This is another thing I will have to solve more generally and do not have yet a very clear answer to.

(A friend of mine remarked while proofreading this post that I should also have taken into considerations my friends' and relative's reaction to my announcing that I was starting the potato diet. He himself had a severe disgust reaction when I mentioned it to him.

I am still unsure how I should have factored this into my decision)

Low risk assessment

I was already doing self-experiments a lot, as it fits my general vision for applied transhumanism. For instance, I take nootropics like ALCAR or MSM, my reasoning being that it seems generally safe and that I want to explore my own configuration space.

I still stand by this. The mistake I made for the SMTM potato diet is not that I should not have tried something like the potato diet. It is that I should not have committed to a full month of this. I think what I should have done is to try a week of it with a very specific approach to it, then note, and take at least a month of break.

In general, I should fragment my life interventions more, trying different costless variants, then easing more into the ones that seem successful.

Mood management

I learned that some things, such as where I live, what I eat, who I talk to, etc... can have drastic impact on my mood and my bipolar symptoms. I will focus more into way I might impact my mood with alimentation, for instance maybe fasting a day could help improve my mood a lot when needed.


This was already something that was on my mind for a while. Scott writing against pascalian medicine for instance has been a big update I am still processing. It seems to me that creating a narrative about some isolated points (re: lithium and hypomania) is very easy to do, and it is easy to miss the big picture.

It might be that I should be way more cautious about weird hype memes in the lesswrong community in general, and that I am not grounded enough in reality. I will be more cautious in joining such experiments or trying 'weird hacks' from the lesswrong sphere for the time being until I have a more definite answer.


Please DO NOT run your own Onion Diet. At least not the way SMTM has done their potato diet. Be responsible about how the participants are going to follow your study, and how hygienic you are with the resulting data.

If you want to try the potato diet, please please please:

  • Find evidences that it's safe-ish. While I am all in favor of risk computation and trying things that have little risks high rewards, I think the risk of one month of eating nothing but potatoes has been very understated.
  • Have some safeguards. Talking regularly to my brother about the diet was not enough. Have some clear signs you look out for that you are at your limit and should stop now.

I do thank SMTM for having run this study, and I am glad I started it, though I should have stopped it sooner.

Thanks to arthurrainbow, my Big Brother (sic) and others for proofreading this post


33 comments, sorted by Click to highlight new comments since: Today at 9:57 PM
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On one hand, I've been disappointed with SMTM's handling of this study. I would rather have had more caveats, more pushes to make people more responsible for their own health, and more contextualization around crash diets and monodiets.

On the other hand, I want this data. And I want more experiments in general. When I tried to run my own study, for a much smaller ask than a monodiet, with what I view as acceptable amounts of caveats and contextualization, I really struggled with recruitment and subject follow through. That's partially a function of audience size, except my smaller audience is in part downstream of me being more cautious and less sweeping in my claims in general. I'm just less fun to read than Slime Mold Time Mold.

[it didn't help follow through that I was specifically recruiting people with ADHD, who are hell's own subject group, but the issue with recruitment was audience size and excitement]

This doesn't undo any of the damage done by SMTM's lack of caution (it feels unfair judging them on your specific case because they did tell you not to do it, but I'd independently noticed less caution and caveats than I'd like). But if we want this kind of data at all we either need to accept those costs, or become more willing to participate in experiments with accurate caveats.

it feels unfair judging them on your specific case because they did tell you not to do it

I notice I'm very confused. SMTM said not to do it because of bipolarity:

Yeah, we would actually recommend people with bipolar disorder not enroll, both because there might be interactions with medication (especially if we’re right about the lithium thing) and because the potato diet seems to sometimes trigger hypomania even in people without bipolar

(The reason I chose to do it is that I am not under medication and that I am type 2 bipolar, not type 1)

I did end up with more pronounced bipolar symptoms - which I included here to give an exhaustive list of effects the diet has had on me - and that was fine for me because I was warned of the risks and that I had done a risk analysis based on this.

My concerns about refeeding syndrome and physical weakness, as far as I know, have nothing to do with bipolarity. Also, as far as I know, no permanent or drastic damage has been effected in me by all this. I am not writing this so much to say "this went very poorly" but much more that "this could have gone way worse"

I want more experiments in general

Maybe I have not been explicit enough about this, but I do too. There is a reason I was excited to sign up, and I am still very enthusiastic about decentralized science. One of the concern I had in publishing this is that I do not want for the cost of such groups to run an experiment to be too high.

I want this data

(I am a little unsure how exploitable the data are at the moment, besides the weight loss. I think this is in big part because of the exploration/exploitation uncertainty mentioned above, and that had they gone in either direction more clearly, the data would have been a lot more useful)

But if we want this kind of data at all we either need to accept those costs, or become more willing to participate in experiments with accurate caveats.

So to be clear: If SMTM had written in big capital letters "we have not researched into any of the following:

  • The best practices to stop a diet
  • Whether potatoes are safe to consume in big quantities for an extended period of time
  • What kind of signs to look for that are clear indications you should stop
  • More research to shrink our unknown unknowns

If you sign up for this diet, you understand that we do not know anything and have no ideas about any of these points or any others that are not mentioned in our post."

Then I would have been completely fine with it. My issue is that there were little to no communication about either what was unsafe, or their level of knowledge about the safety of the diet.

Also, this would have been less problematic for me if they went fully into the "explore" route and were not doing this study as a mean of replication (no set period of time, full communication between participants, frequent updates about the diet, etc). This issue is more relevant for the "please sign up and fill this form" type of study

Part of me strongly agrees with you. At the same time... I don't think "how much work would it have been to address [single bad thing]?" is the right unit of measurement. The actual question is "what would the cost/benefit analysis of address every single thing in this class of problems?", and that's a lot less clear cut. 

Some things that make it difficult:

  • There are just a lot of potential problems.
  • There are an infinite number of things they didn't research. Every time they add one to the explicit list of unresearched things they make the list as a whole harder to read (-> people are more likely to miss warnings relevant to them) while also conveying more safety and confidence. God forbid people decide anything not on the list of "things we didn't check" was in fact checked.
  • You can say they should estimate the danger from each of these and only explicitly disavow research over a certain level of importance, but that's an inherently noisy process people are likely to disagree on, and no matter what there has to be something just below the line. So again adding warnings can leave people with an inaccurately increased feeling of safety.

When I share medical info, I always preface it with "anything with a real effect can hurt you, think this through for yourself". I think that's a little better than what SMTM did. But I don't see any easy additions to their statements of "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" and "We are not doctors. We are 20 rats in a trenchcoat. eee! eee! eee!" that make things obviously better.

You note that you felt obliged to keep going in order to provide better data. Maybe there was pressure in private communication, but AFAICT they explicitly spoke against that in the blog post. I had a similar thing happen in my experiment- despite explicitly saying people could drop out at any time and would still be paid, one person was extremely reluctant to do so despite bad side effects and needed a strong push from me. In some sense I don't think this is fair to put on experimenters, people shouldn't even need to be told "stop if you feel bad". But this seems like a pattern, and therefore should be taken into account even if it's not objectively fair. 

"what would the cost/benefit analysis of address every single thing in this class of problems?",

I mean, that is why I included "More research to shrink our unknown unknowns" as a general category. I do not think the research needs to be thorough, 3-4 very broad general area would suffice, but even if that does not fit into the points you mention, a statement along the lines you mentioned could work. In general, I do not think that more than one-two hours should be spent on writing this warning.

As for "If at any point you get sick or begin having side effects, stop the diet immediately", that is indeed a good first step. My problem with it is that I am now understanding that you can develop side effects that indicate one should stop, that are not apparent unless you really track several variables intently. A general instruction to, in addition to doing one's own research, decide what to look for in advance could have worked.

You note that you felt obliged to keep going in order to provide better data

I want to note three things:

  • I did not feel pressured by SMTM either in their public or private communications at any point
  • That is not quite correct. I wanted to keep going for the data to be included as a data point, especially if the diet turned out not to work, which I thought it would not.
  • I had not noticed any side effects or problems at that point. I was tired of potatoes, but it was manageable.

Maybe I should better emphasize on what points I feel SMTM is responsible and on what points I do not. I do not feel that SMTM is responsible for my safety and what could have happened, or the impact of the diet on me. In fact, I do not believe SMTM to be responsible for anything me-related: I made my own choices, and the fact that I did not stop the diet sooner was my own mistake I am owning up to.

What I do feel is that SMTM had a very loose methodology in how they conducted their studies, were more trying to confirm their hypothesis than really challenge it, and as a result the data is quite muddled and probably not that useful.

The safety part is related in the sense that:

  • It might be that many potato diet's benefits are actually just coming from malnutrition. But if there were evidences of safety, that would not turn up to be a problem
  • It is relevant about what kind of preemptive research they made to decide whether the potato diet was worth it
  • For me at least, it goes with the general notion that it was very unclear what they were looking for

Re solanine poisoning, just based on what's written in Wikipedia:

Solanine Poisoning / Symptoms

[...] One study suggests that doses of 2 to 5 mg/kg of body weight can cause toxic symptoms, and doses of 3 to 6 mg/kg of body weight can be fatal.[5][...]

Safety / Suggested limits on consumption of solanine

The average consumption of potatoes in the U.S. is estimated to be about 167 g of potatoes per day per person.[11] There is variation in glycoalkaloid levels in different types of potatoes, but potato farmers aim to keep solanine levels below 0.2 mg/g.[18] Signs of solanine poisoning have been linked to eating potatoes with solanine concentrations of between 0.1 and 0.4 mg per gram of potato.[18] The average potato has 0.075 mg solanine/g potato, which is equal to about 0.18 mg/kg based on average daily potato consumption.[19]

Calculations have shown that 2 to 5 mg/kg of body weight is the likely toxic dose of glycoalkaloids like solanine in humans, with 3 to 6 mg/kg constituting the fatal dose.[20] Other studies have shown that symptoms of toxicity were observed with consumption of even 1 mg/kg.[11]

If 0.18 mg/kg = 167 g of Potatoes, then 1 g/kg is reached at 927g of potatoes, which equals about 800 calories. So if you "eat as much as you want", I'm not surprised at all if people show solanine poisoning symptoms.

(And that's still ignoring probable accumulation over prolonged time of high consumption.)

The more I think about it, the more I wonder if boiling the potatoes infused them with the peels and increased significantly the quantity of solanine I was consuming. An obvious confounder is that whole-boiled potatoes are less fun to eat than in more varied forms, so it doesn't discriminate with the "fun food" theory

Thanks a lot for the estimate, I'll look into recent studies of this to see what I find!

The potato diet works for well-understood reasons that are entirely accounted for by mainstream obesity science. The brain's appetite regulation circuits are highly responsive to calorie density, macronutrient variety, salt, food variety in general, and other things which are all minimized by eating only potatoes. The putative connection to lithium is grasping

Did you, by any chance, predict this result anywhere? Explanations after the result are a dime the dozen.

Here is Stephan Guyenet writing about the diet 10 years ago:

This seems useful and I liked the author's book but I wouldn't call it "well-understood reasons that are entirely accounted for by mainstream obesity science". If anything, the fact that we've known about it for >10 years and it hasn't spread widely suggests to me that it's unlikely to be a silver bullet.

ETA: I’d completely misunderstood Elizabeth’s comment. This comment I wrote does not make sense as a reply to it. I’m keeping my comment here with this disclaimer on the top because I wanted to make these points somewhere, but keep that in mind.

the fact that we've known about it for >10 years and it hasn't spread widely suggests to me that it's unlikely to be a silver bullet.

I don't know exactly what you mean by "unlikely to be a silver bullet," but I want to outline the reasons I think this diet is nowhere close to being a $20 bill lying on the sidewalk, as some people seem to think it is:

  • very restrictive diets are very socially costly to follow. If you regularly eat from college dining halls, cafeterias at work, restaurants, other people's homes, etc. you'll have a very hard time following an all-potato diet. Compare it to being vegan — outside of vegan-friendly places, it can be quite inconvenient to be one, and following an all-potato diet seems like it would be significantly worse than that. 
  • very restrictive diets might cause weight loss that is too rapid to be healthy. Losing weight too quickly increases your chances of getting refeeding syndrome (if/when you go back to eating normally) and gallstone formation by quite a lot.
  • It is unclear that this diet doesn't have the same exact problems as all other diets, that is, a high attrition rate[1] and weight regain upon cessation. 
  • Investigating diets seems relatively uninteresting when (1) diets have a huge attrition+weight regain problem and (2) semaglutide and tirzepatide alone would massively reduce obesity rates if they were more popular, and there are drugs in preclinical trials that seem even more promising 
  1. ^

    I hope no one is taking the attrition rates calculated in their post at face value, given that all of their data is from people who literally signed up for a potato diet and hence there is a very obvious selection effect at play. Even if you do take them at face value, however, the attrition rate was like 40%-60% after 4 weeks, depending on how you slice it, compared to 18.8% after 3 months in this study that they mentioned[2], and ~30-50% per year in general in the diet studies they talked about.

  2. ^

    They cited this study as having a "56.3%" attrition rate. I think they were probably referring to the fact that the attrition rate was 53.6% (not 56.3%) after 12 months. I don't know why they chose to report that number, when the study also reported a 3-month attrition rate, which is much closer to the timescale of their own diet. 

I think I used "silver bullet" to use the same thing you mean by "$20 bill", so we're in broad agreement. I also don't personally know anyone who thought this was definitely a slam dunk; everyone I've talked to has had the attitude "sounds crazy, generally good to try things".

I agree with you that the weight loss may be too rapid to be healthy, and that the data is basically worthless without knowing what the rebound rate is. I also dislike the emphasis on weight loss over 24 hours, when it's impossible to have one-day weight loss that is both noticeable above the noise in the measurement and healthy. 

I disagree that it being prohibitively restrictive for many people is a reason not to investigate. The restrictiveness and social costs aren't secret harms people won't notice until it's too late; people will naturally notice those costs and change their behavior if it's not worth it. SMTM claims the diet tolerates a lot of deviance, so the costs may be quite low. Maybe that slows the weight loss, but people can make their own choices on that. It seems much more forgiving than keto, where one carb too many breaks the diet for days, and despite a very high attrition rate there's a substantial number of people sticking to keto long term.  The high attrition rate is irrelevant to knowing if the diet works when you stick to it. 

I would feel differently if they were charging a large up front fee and blaming people for not sticking to it, but that is not at all happening. They're suggesting people eat a very cheap food and stop if they don't like it. This might change if potato fat camp happens, at which point I do hope they highlight the drop out rate, but I really don't see "you might quit" as a reason not to try.

I also disagree that we should wait for drugs. Those are definitely worth investigating, but the history of weight loss drugs and especially drugs in trials is really bad, not to mention none of them are as widely available as potatoes.

I still think the potential silent risks are a reason to be concerned. I doubt their reports that potatoes have enough protein, especially for highly active people, and expect micronutrient shortages as well. I hope a more formal study checks those. I didn't try the diet because there was absolutely no chance "100% potatoes" would be healthy for me, and I advised the friend who asked to wait on the data. I put an extremely large probability on "this is just another fad monodiet and it's bad in the ways they are all bad". But trying it out, especially in the extremely flexible way they are, still seems good to me.

Oh my, I completely misunderstood your previous comment. I apologize.

very restrictive diets are very socially costly to follow. If you regularly eat from college dining halls, cafeterias at work, restaurants, other people's homes, etc. you'll have a very hard time following an all-potato diet.

To be fair to SMTM's potato diet, the idea is that it still works even if you cheat a lot.
That was somewhat my experience with the diet though, it makes social interaction a lot more awkward

semaglutide and tirzepatide alone would massively reduce obesity rates if they were more popular

I mean, the idea of a cheap, not very effortful and efficient life intervention still appeals to me. It might not be the most pressing problem, and it might not solve global obesity, but if it indeed does give a boost of energy in a safe and reliable way, that is already worth knowing.

The reasons are well-understood. It hasn't taken off because eating nothing but potatoes seems extreme and weird to most people, and even less appealing than other diets

But people try lots of weird fad diets. Moreover popular wisdom seems to be capable of having different reactions to different fad diets- grapefruit diet is considered dangerous and you'll regain the weight immediately anyway, but keto is considered to sometimes work if you can stick to it, which is pretty hard. It's not clear to me keto started off obviously distinguishable from other fad diets of the time- but it worked for some people and was sustainable for some people, and so grew in prominence,

TBC I don't think eating only potatoes is long term healthy. If the weak form of potato diet- where you eat some potatoes every day but are otherwise unrestricted- works, that is substantially easier to follow and less weird than a lot of popular diets people stay on for years. 

I am highly skeptical because that's the correct default stance to have towards monodiets claiming dramatic levels of weight loss, but if it worked in a healthy sustainable way I don't expect weirdness to kill it.

I agree that the connection to lithium seems pretty weak, although it's possible there's still something special about potatoes (maybe potassium?). The two weird things with the potato diet are the increased energy (the opposite of how most diets work?) and that it seems to work fine even if you "cheat" constantly. Note that olive oil and (lots of) salt were recommended as part of this, so I think most of us weren't eating bland boiled potatoes.

That said, it's possible the only special thing here is that potatoes are just really convenient for a no-variety diet.

It's mostly the latter, it also helps a lot that potatoes are pretty micronutrient-replete and low calorie density compared to other bland, starchy staples. I would expect a diet of nothing but rice, steamed chicken breast, and steamed broccoli to have similar effects. This is of course close to how physique enthusiasts have learned to eat to lose fat.

For the weirdness around how they did this / didn't preregister, I thought they were pretty upfront about how this was exploratory (trying to generate hypotheses and see if the effect is plausible, not confirm a hypothesis). The next step would be a more serious experiment like the Potato Camp they mentioned.

Doing it this way lets them figure out what to focus more expensive / complicated studies on without wasting time and money (like if they ran a big experiment without peeling the potatoes and it ended up being a complete waste).

I think doing this kind of thing is really important because trying to make everything safe means we frequently don't do useful science (see: we let millions of people die to avoid letting volunteers take risks in vaccine studies). Doing more mad science is a useful correction. That said, I think it's important to remind volunteers that they shouldn't keep going if the mad science is hurting them. I get the impression SMTM was trying to tell people this but they probably should have been more direct about telling people saying they're not feeling good to stop.

The next step would be a more serious experiment like the Potato Camp they mentioned.

This is puzzling to me. Randomizing people to different kinds of somewhat restrictive diets[1] seems like a way cheaper and more obvious experiment to test some of SMTM's hypotheses, such that the potassium in potatoes clears out lithium or whatever. 

It seems to me that they would have incurred little additional cost if they had randomized people in this study they already did, so I am somewhat confused about the choice not to have done that.

  1. ^

    I say "somewhat restrictive" because I'm reluctant to advocate very restrictive diets, given the very low caloric intake reported by some people in SMTM's blog post, and the increased risk of gallstones and refeeding syndrome that people incur by eating that little.

Then shouldn't it be weirder? Like, having full open data, not trying a month specifically and varying this, etc?

I think doing this kind of thing is really important because trying to make everything safe means we frequently don't do useful science

That is a very good point, and I agree.

Two things on this point:

  • It did not seem to me that SMTM marked this as clearly unsafe, but I am not neutral enough to know. Just: There is a difference between "quit if you feel unwell" and "This might have drastic negative impact on you you will not even notice or feel"
  • While mad unsafe science is cool, it is a good idea to make it safe_r_. For instance, SMTM did tell us to take vit A and B12, which was warranted. The same way, other precautions, specifically about how to quit the diet, could have been mentioned

It might be that I over-updated though.

What data do you think they should be sharing that they aren't? They did put a dataset up somewhere.

Right, I must have phrased it poorly.

What I mean is that if the goal was just to explore, and modifying the diet while doing it is not a problem, then it would have made more sense to have access to everyone's data as they were doing it (at least between participants). Also have more ways to communicate between participants to share our experience, tips and tricks, etc...

I wouldn't have made participation mandatory (and I expect you wouldn't either) but a way for participants to opt-in to a community does seem valuable. Maybe they thought that was covered by twitter? A lot of people did seem to be discussing it there.

I thought they were pretty upfront about how this was exploratory (trying to generate hypotheses and see if the effect is plausible, not confirm a hypothesis).

Also, yes, that was my impression as well and what I signed up for. It's just that a lot of features of the study directly clash with this exploration.

(I also disagree that their results are that remarkable.)

Edit: By remarkable, I mean "shows that it is specific to potatoes"

What’s a “chisp”?

Typo, I meant chips/crisp. Thanks!

Nobody here seems to have offered an unreserved defence of SMTM, so let me do it:

  • SMTM told the author of this post they advised against it, they still did it, and were happy with the result.

  • The author says "I don't think that SMTM has done enough to show that it was safe". But I notice that I am confused, because it is not the job of SMTM to make this study 'safe', whatever that means. The world is not "safe", and everyone is an adult, and adults should use their own judgement when following random internet advice. If someone regrets unreservedly following random internet advice, they got a valuable life lesson. There's no reason to think SMTM knew about and tried to hide information about Solanine poisoning, so it's unfair to make it seem like they are responsible when the participants could have equally well found out about it themselves. The author wishes SMTM had put up a neon sign, but their blog heading literally has "Mad Science Blogging" in it, isn't that enough of a neon sign already? .

  • Pre-registration wasn't really important, publicly announcing a study and getting participants who care about the result is a form of pre-registration.

  • Just because data isn't perfect doesn't mean it isn't valuable (even if it does nothing but teach the community what kind of data it makes sense to to investigate if you do something like this ).

While the "safe" point you/they make is absolutely crucial to the whole endeavor, nobody seems to be discussing the main underlying "promise" that such an experiment holds, and that they have repeatedly stated as being one of the main drivers in their experiment : namely, that the "potato diet" seems to have a profound effect on regulating the sensation of satiety, even after the diet.
This fact is new and unheard of with most, it not all weight-loss diets. This is not something you expect from a monotonous diet with rapid weight loss, much less so from a monotonous diet with rapid weight loss where you also cheat a lot. The section 7 of their report on the diet's results is clear: something is happening with many people's hunger feeling, and we don't know why. Alas, it did not concern OP (although he seems to have had a "dissipation" of hunger at some point) but that's still worth exploring.

“Eat nothing but 𝑋 for 𝑛 weeks” diets (where 𝑋 is a single food item that isn’t a meal replacement) are pretty bad diets that we wouldn’t want to follow even in the cases where they are effective at losing weight, which when they are they probably are for all sorts of bad reasons. You have more important concerns than losing weight. I wouldn’t follow such a diet for one week and would pay a good amount not to have to follow it for four weeks or longer periods of time; I don’t think people should be willing to participate in such studies for free.

That it’s an all-𝑋 diet is the biggest problem, but potatoes are also not a great choice: they have high glycemic load and worse nutrient content than many non-starchy vegetables, they make you feel hunger again, meaning you’re probably going to eat too much, and they contain dangerous poison, and removing that poison means you have to peel them to some extent meaning you lose a significant amount of what nutrient content they do have. Their proportion of the amino acids our body can’t synthesize itself satisfactorily and their protein digestibility aren’t bad, but there are better sources.

they have high glycemic load and worse nutrient content than many non-starchy vegetables, they make you feel hunger again, meaning you’re probably going to eat too much

What do you make of all the claims that people didn't feel hungry on the diet then? Placebo effect?

Isn't it common for people who fast for more than 3-5 days not to feel any hunger? I wonder if there's a similar mechanism here

Other than water, potatoes are mostly starch, which becomes easily digestible after cooking. This makes your blood sugar level go up and down fast and makes you feel hunger quickly after eating them. I don’t know the implications of eating potatoes on a long-run effect on how hungry you feel generally.