The Mysterious Case of Outlier 17

If you’ve followed my blog, you’ll know that I originally got inspired running these experiments, and writing about them, by Slime Mold Time Mold and their potato diet trial. While I didn’t formally participate in this trial, I did an informal version, but I only made it 17 days and didn’t lose any weight.

The SM TM half-tato trial

A few months after the 100% potato diet trial was over, they started another one: this one was 50% potato, 50% eat whatever you previously ate. They called this the Half-Tato trial and they released the results a few months ago.

In short, people on the half-tato diet lost 1.7lbs on average over 30 days. Here’s a histogram of the number of people losing/gaining specific amounts:

Ok, cool. Seems like most of the people seem to be clustered around- waaait a second. What’s that all the way on the left? Did somebody seriously lose.. what is that.. 17lbs eating 50% potatoes for 28 days?

For reference, I think that -17lbs would put this participant in the top 5 (out of 64) of the full, 100% potato trial, and #1 in the ex150 trial. And she was doing only 50% potato.

To show you another view on how much of an outlier this is, look at this graph of people’s weights on the half-tato study over the 28 days:

Starting on day 7, Outlier 17 (as I call her) overtakes the rest of the pack, never to be seen again. She crosses the -10lbs line on day 13. Nobody else makes it to the -10lbs line, ever. By the time the trial finishes, she’s lost nearly double the weight of the #2 participant.

Because she is such an outlier, SM TM reproduce a lengthy excerpt from her experience report, which I will shamelessly copy & paste in full here:

I signed up for a spreadsheet for 52 weeks.  I’m doing the diet and have had great success … Am female with 100 or so lbs to lose (now 30 down).

I first lost about 15 lbs doing a very loose version of potato by default after first reading your blog pre half tato experiment and have since lost another 15 beginning April 22 with starting half tato in earnest.  I steam peeled yukon gold in batches in the Instant pot for 12-15 minutes at high/manual (depends on size, I try to get bigger but often its just medium available).  Right out of the instant pot I add white vinegar which helps preserve color and appearance and tastes great later (more subtle than adding vinegar at mealtime) before cooling and fridge.  I started eating a mix of cold and hot depending on if microwave is available (sometimes with mustard) but now I’ve settled into just hot (2 min microwave) with mainly salt.  I try to have this 2-3 meals out of the day (2 medium or 1 big 1 smallish per meal).  One of the 2 potato meals I may add one of:  poached egg yolks; calf liver lightly sauted in butter (plus lingonberries and/or honey); or cooked ground beef (with 21 gun salute seasoning from trader joes and sometimes full fat sour cream), and possibly pepper or cholula sauce (rare), occasional oysters (fresh or canned).  I don’t add ketchup (except once – when I went out and had beef fat fries at a steakhouse bar which did not seem to stall).  I really enjoy the potatoes and look forward to them.  I am not hungry but feel satisfied.  I also have dairy – at least one glass of milk a day (either raw whole milk or 2% or whole conventional) – and a small amount of juice or lemonade.  Some mornings I may have full fat yogurt with collagen and stearic acid (see fireinabottle.net) but not all mornings.  I have some extra potassium as well as other supplements.

So not only did she lose 17lbs in 28 days of half-tato, she actually lost 15lbs before that, doing essentially the same thing!

And she’s supplementing stearic acid from Fire in a Bottle.

If anyone’s enough of a Brad Marshall-acolyte to use stearic acid, you can bet your canola oil she’s avoiding PUFAs like a ninja. “Beef fat fried?” Who even knows what that is, besides PUFA people?

Full-tato vs. half-tato

Overall, how did the half-tato diet trial compare tot he full-tato one?

SM TM say:

Overall, the effect is less than half the effect of the original potato diet. Average weight loss on the potato diet was 10.6 lbs, so half of that would be 5.3 lbs. Instead we see only around 15% of the effect of the full-tato diet.

Very interesting. This ties a bit into the idea of additive vs. subtractive diets.

SM TM (from what I can tell) think of the potato diet as an additive diet - there’s something you’re missing, and if you eat enough potato, you’ll get it. The potatoes are essentially a supplement. Their main suspect seems to be potassium, and they previously ran a potassium supplementation trial.

I tend to think of diets (at least fat-loss diets) as subtractive. What gets cut out of your diet when you eat only potatoes? And what doesn’t if you only eat potatoes 50% of the time?

Let’s square off full-tato vs. half-tato on my list of hypotheses:

• Low-protein: check. 100% potato is extremely low in protein. 1,000kcal of potatoes only have around 25g protein, so just about the same amount as ex150.
  Why would eating low-protein help you lose weight?
  
  Maybe a contraindication: Outlier 17 seems to have consumed quite a bit of protein. It’s not clear exactly how much, but she was eating beef, yogurt, milk, eggs, collagen.. it clearly wasn’t nearly as low-protein as the full potato diet.
  

• Low-PUFA: It really depends on both your regular diet, and how you prepare your potatoes.
  
  The average American eats 20-25% of total calories as PUFAs. You could probably achieve that on a 100% potato diet if you only ate french fries fried in seed oils.
  
  But if you boiled, baked, roasted, or steamed your potatoes, you’d probably get zero seed oils. Even if you sauteed them in seed oils, you’d get way less of it than on the SAD.
  
  Now a few people in the original full-tato study do report regularly frying their potatoes with oil, and some report eating commercial french fries on occasion. Apparently, people were especially fond of Five Guys fries, which are reportedly fried in peanut oil. Now peanut oil’s not great in terms of PUFA content at 32%, but it’s not soybean oil (nearly 60%).
  
  But one of the french fries people says he ate them for 3 meals in a day “on a couple of days.” It’s not clear that people were exclusively living on PUFA-fried french fries, which is just about what you’d have to do to achieve the amount consumed on the SAD.
  
  And the couple of descriptions of sauteing potatoes in oil mention using about 1 tbsp of oil.
  
  Finally, one participant in the original all-tato study actually reports not losing any weight during the first 2 weeks, while using olive oil. The following 2 weeks, removing the olive oil, voila - lost 10lbs. Now I don’t consider olive oil a seed oil, but it does contain 10% PUFAs. Who knows.
  
  Still, it’s not as obvious as the low-protein case.
  

• Low-palatability: you could definitely argue this one. A 100% potato diet consists of.. well, 100% potatoes. That’s about as mono diet as it gets. On a 50% potato diet, you can eat a few potatoes and everything else.
  
  Unfortunately, palatability is difficult to measure or even define. Outlier 17, the person who lost by far the most weight on the half-tato diet, regularly ate full-fat yogurt, drank full-fat milk, ate egg yolks poached in butter, beef liver, ground beef with sauces and spices, full-fat sour cream, and oysters. Oh my, the poor thing!
  
  And, the fries. Now I personally don’t like fries, never have. But normal people seem to really like fries. They’re practically the epitome of “ultra-processed, hyper-palatable” junk food. I mean it’s fries, c’mon.
  
  Inconclusive. I’d say if Outlier 17 had eaten 50% potato and 50% boring gruel, sure. But she seems to dispel this hypothesis a little bit.
  

• Low-carb: Yea, maybe not.
  

One last hypothesis that’s interesting, if not one of my main ones: if you’re obese, you can’t eat fat AND carbs. You have to pick one and keep the other extremely low.

This is a theory I’ve recently heard a lot about. There’s something called the Randle cycle, a mechanism in our cells that regulates how much fat vs. glucose the cell will burn. It appears that, at least in metabolically broken people, this can become a bottleneck when consuming a diet both high in carbs and fat.

So maybe you can pick an extremely ketogenic diet, like ex150, where 88% of calories come from fat. Or you can pick the potato diet, which is the exact opposite: 91% of calories come from carbs. Both are extremely low in protein.

Having to pick fat OR carbs, and eating extremely low protein, might not be necessary for a metabolically healthy individual. But maybe, due to some mechanism, it helps lose weight if already broken?

In conclusion, there are some good leads here on what could make full-tato so much more effective than half-tato, but it’s not exactly obvious, and each of them seems to have some contraindications.

Zooming in on Outlier 17

One thing that caught my eye was the vinegar. One contestant on the ex150 trial had mentioned making an “illegal carrot salad” each day with vinegar, and I learned that this is a Ray Peat thing. Some low-carbers, too, swear by using vinegar to improve insulin resistance.

She also supplements potassium - in a way, combining two SM TM trials into one, as they also ran a potassium supplementation trial.

She consumes plenty of full-fat dairy, although it’s not a super high fat diet per se. But the fat she does get is highly saturated, including dairy, coconut, and pure stearic acid.

But the question that plagued me the most: how long had she been following FIAB? Had she been avoiding PUFAs and/or BCAAs? For how long?

So, of course, I contacted her.

Interview

Outlier 17 was nice enough to answer all my questions in detail.

Have you been doing the low-PUFA/TCD/Fire in a Bottle approach? How long? Could you describe in detail?

I became somewhat conscious of Omega 6 v Omega 3 ratio about 10 years ago via a Dave Asprey/Cate Shanahan podcast, plus my gym was doing a Whole 30 challenge, and I threw out all my vegetable oil at home (other than MUFA) and tried to eat more salmon or cod liver for a period, thinking that should fix the ratio for the Omega 6 foods I continued to eat.

For example, I still ate out a lot and sometimes had fried foods and mayo based things when eating out (blue cheese dressing, Hawaiian macaroni salad).

I did find FB [Fire in a Bottle] blog a couple of years ago and it really put together for me the idea of PUFA as absolute bad guy, rather than giving me an out to rationalize french fries if I also had sardines.

FB also made me more aware of issues around chicken and pork fat (I'd been liberal with skin, lard, avocado before), as well as the connection to PUFA and metabolism.

I gained weight trying to implement FB principles unfortunately, and any increase to temperatures was fleeting. I don't knock the diet - maybe I didn't do it right or quit too soon - but I also found it a little amorphous to know if you're doing it right versus "eat potato" which for some reason resonates with me. FB was satiating, but so is potato without eating as much fat.

I next tried implementing some Ray Peat principles, since I was interested in the idea of increasing temperatures after learning about the reduced demographic metabolic rates from FB.

I also really like the Ray Peat people, but at least however I was doing it, I just got fatter and temps didn't budge in any sustained way. Will fully admit I wasn't diligent with any of this - during COVID and up until the end of April I was going out to eat several times a week and wasn't completely avoiding fried or mayo related foods.

Would you say that after avoiding PUFAs for a while, your experience dieting/losing weight was different than before?

Maybe? My first 15 pounds (pre-study) were done pretty lazily and I still ate out or take out a few times a week and it didn't seem to matter on any given day.

As long as that particular day I ate 50%ish potatoes I might still lose 1/3-1/2 a pound that day, even if that weekend I ate at a restaurant. But when I really cut out take out/restaurant dining and did potato every day the loss definitely went faster.

On the other hand, in my pre-potato trial time in mid April I did a week of mostly Bulletproof style including limited carb while at an event where I mainly didn't choose the food and I still didn't lose any weight, despite no PUFA.

How would you say the potato diet interacted with PUFA-avoidance, both in terms of practicality and also did it feel like they helped each other work?

It makes life easier when you're not hungry and potatoes are very satisfying. When in doubt, potato.

When you are at work and need a bite, it’s easy to have thrown some cold potatoes into a tupperware that I can just easily heat in a microwave.

When you get home from work and don't have the mental energy not to get take out or can't figure out what to cook, it’s a relief to know you can just have potato (and whatever else you want to add if you have it, but no pressure.)

When I eat at home it's pretty easy for me to be low PUFA since I don't keep it around (except eggs). It's also nice not having the pressure to make a more "balanced" meal when you're tired during the busy work week, knowing that the potatoes themselves have a lot of nutrition and if you need to gild the lily on the weekend when you have more time you can add some super foods like liver, or yolks, or oysters.

Potatoes also keep in the car or at your desk and don't get gross (I pre-vinegar them anyway); even if you can't find a microwave they're not too bad cold if you have a little salt and mustard which is easy to get. The only PUFA or MUFA at home is when I cooked some copper river salmon (just one for the season) and wagyu sirloin, plus egg yolks (although I get corn/soy free).

How high was your protein intake on the half-tato diet?

There is some overlap with what Brad [of Fire in a Bottle] is doing, although I didn't consistently go super low protein, as I often had dairy although not buckets of it. But I didn't eat lots of meat, sometimes none, and if I did it usually wasn't more than 4 oz.

I didn't prioritize protein since meat other than liver doesn't seem to get a lot of bang for buck on nutrition, and I didn't feel like eating huge amounts of potato to even it out so it was easier to just have some milk or sometimes yogurt/cottage cheese to make sure I got nutrition covered, plus occasional liver or seafood/oyster (also knowing that potato is pretty complete for lots of nutrients helped).

I had collagen or glycine a few times a week but not daily

2 servings of dairy was the norm. And it was usually 2 percent or whole although the protein difference is marginal. And the yogurt was whole normal (not nonfat Greek which is probably higher protein) maybe 3x a week and cottage cheese was 4 percent maybe a couple times a week at most. And sometimes a little raw Gouda or sour cream. Plus sometimes 1-2 eggs or 4 oz meat but not every day.

I think the range was around 22-70ish grams of protein a day, more often closer to 38g, and the 70g a day might have been 1-2 times a week.

I also scrolled through a few more macro breakdown days in June and they seemed in this range, although later in June and early July it seemed more 50-70g.

Thoughts: PUFA not big in the short-term, but long-term factor? Low protein?

The mysterious case of Outlier 17 - solved?

Well, maybe not quite solved. But now that we’ve dug in a little deeper, it fits rather neatly into our mental model, doesn’t it?

Here’s what stood out to me:

1. She had been restricting PUFAs for a long time, but only got super serious about it a few months before trying out the half-tato diet.

2. She had limited success or even gained weight mixing carbs + fat (“The Croissant Diet” and Peat stuff) even while heavily restricting PUFAs.

3. Her protein intake of 22-70g/day was extremely low, possibly even lower on average than ex150’s 40-50g day.

If you told me “Hey, this one participant lots way more weight eating 50% potatoes than anyone else” then this is pretty much what I would’ve predicted at this point.

In fact, the full potato diet meets all 3 of these points: no PUFAs in potato, very little fat overall in potato hence it’s mostly carbs, very little protein in potato.

After my own experiments and Brad’s work at Fire in a Bottle (not to forget the awesome people of r/SaturatedFat), this is my current mental model of obesity:

1. Excess PUFAs are the root cause. You likely have tons of them stored in your body. Cut down to zero as much as possible. De-PUFAing yourself starts showing effects a few months in, but takes years to complete.

2. While PUFA’d, there’s a 35% chance you’ll have to restrict protein. Not everyone seems to have this issue, but many do. This is why I originally made ex150 so low protein. In fact, I called it “low-protein keto” to myself the first 2 months.

3. While PUFA’d, there’s a 75% chance you’ll have to pick either fat OR carbs, and get 80%+ of your food from the one macro. Call it Randle cycle, call it something else, but most people don’t seem to be able to lose weight on a mixed fat+carb diet while they’re still metabolically broken. Both ex150 (85%+ fat) and potato diet (90%+ carbs) seem to work pretty miraculously for a wide variety of people.

And so Outlier 17 did everything ex150 did, except with potatoes instead of cream. You could say she was doing Brad’s new Glass Noodle Diet, which is pretty much the carbosis equivalent of ex150: no PUFA, very low protein, most of your food is carbs low in BCAAs. Only she did it before Brad even invented it.

Of course you can’t prove a hypothesis by providing more examples of where it was true, but it is a nice indication that we’re onto something here, it fits our curve.

To really disprove parts of this mental model, we could try the following things:

1. Half-tato/cream diet with high vs. low protein group (tests protein/BCAA)

2. Half-tato/cream diet with lots of seed oils added vs. no seed oils (tests PUFA)

3. Half-tato/cream diet with the other 50% from the same macro (tests Randle cycle)

Alas this seems to give us a matrix of 8 possible diets to try.

Here I want to give a shout out: Reddit user springbear8 has started registration for a community trial of Fire in a Bottles new Glass Noodle Diet. If you’re interested in trying out a high-carb, low-fat, low-protein, no-PUFA diet, please sign up! You might help science, you might lose 17lbs in 28 days, you might make friends along the way.

Finally, big thanks again to Outlier 17 for her detailed answers. Hopefully, this helps shed some light on her miraculous success on the half-tato diet.

After Outlier 17 proofread this post, she had a few comments:

She does think it could still be potassium/lithium, as originally suspected by Slime Mold Time Mold, or something else in the potatoes.

Additionally, her fat percentage was actually in the 30-40% range, and thus she was mixing carbs + fat. But the absolute amounts were relatively low because she was eating absurdly low calories each day, often times below 1,000kcal/day.

In a way this makes sense. If we assume her 17lbs fat loss during the 28 day half-tato trial was all fat mass, that would add up to a deficit of (17lbs * 3,500kcal/lbs) / 28 days = 2,125kcal/day. Now maybe it wasn’t quite 100% fat loss and there was some water weight, but even half of that is a shockingly high deficit. Doing this while eating ad-libitum and feeling satiated tells us she had plenty of access to her body fat reserves.

This is what we’d expect to happen in the simple CICO model if somebody woke up obese one day: they should eat very little, have almost no appetite, and lose the weight rapidly.

The real mystery of Outlier 17 seems to be: what exactly is it she did to unlock this “reversing obesity” mode, and why isn’t it the normal case for people dieting?