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Summary of the diet used in the study via ChatGPT4:

IF-P Diet Instructions:

Protein Pacing Days:

• Women: 4 meals/day; Men: 5 meals/day.

• Meals: 2 shakes (breakfast + one), 1 whole food dinner, 1 afternoon snack (men only), 1 evening protein snack.

• Calories: Women: 1350–1500/day; Men: 1700–1850/day.

• Macros: 35% carbs, 30% fat, 35% protein.

• Fiber: 20–30 g/day.

Intermittent Fasting Days:

• Calories: 350–550/day.

• Fasting Duration: 36–60 hours with supplements and snacks.

Protein Intake:

• Each Shake: 30–36 g protein, 9 g fiber.

• Evening Snack: 200–250 kcals.

Even shorter summary:

Eating less energy than the body burns results in burning of stored energy reserves.

> Eating less energy than the body burns results in burning of stored energy reserves

Nope [1].

Even proponents of the energy-balance model clarify that “the brain is the primary organ responsible for body weight regulation operating mainly below our conscious awareness via complex endocrine, metabolic, and nervous system signals to control food intake in response to the body’s dynamic energy needs as well as environmental influences” [2].

Calorie in calorie out is the flat-earth model of metabolism, trading truth for simplicity.

[1] https://www.health.harvard.edu/staying-healthy/stop-counting...

[2] https://www.sciencedirect.com/science/article/pii/S000291652...

Yet, you can lose weight on Mountain Dew and Doritos by counting calories.

  Little Debbie Snacks, Oreos, Doritos and Diet Mountain Dew sure don't sound like diet food. But a nutrition professor at Kansas State University ate only convenience store snacks for two months and lost 27 pounds.

  The key? Moderation.

  Mark Haub kept his food intake below 1,800 calories a day -- no extra exercise required.
https://www.npr.org/2010/11/12/131286626/professor-s-weight-...
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> Each group was given meals with the same number of calories and instructed to eat as much as they wanted, but when participants ate the processed foods, they ate 500 calories more each day on average. The same people's calorie intake decreased when they ate the unprocessed foods.

Your own Harvard link supports the calories in/out theory, but argues against counting calories. Different things.

> own Harvard link supports the calories in/out theory

Calorie in / calorie out isn’t a theory, it’s a thermodynamic corollary. I compare it to flat eartherism because “things go down” is similarly a corollary of gravity. The missed link with the latter is that down isn’t what it intuitively means. The missed link with colloquial energy-balance interpretations is “calorie in” and “calorie out” don’t mean what people think it does.

If you have a healthy metabolism, cutting calories and increasing burn—cereris paribus—should spike a starvation response. That has some perks. But it should also reduce your resting metabolism, sometimes below even maintenance levels; it should increase your absorption and sequestration of energy; it should alter your taste to make calories more appetising, and increase existential anxiety around the procuring of those. (Counterfactial: I’m someone who is fine being hungry. )

Just as one can design short bridges on a flat-earth model and be fine, one can deploy this simplistic model (it’s not a theory, that’s the vastly more complex energy-balance model) to make short-term gains. But it’s fundamentally wrong in that it builds the wrong intuitions. Similar to how thinking of our brains as a steam engine or microcomputer sort of works, in some cases, or if you’re trying to be punchy in internet comments, but is fundamentally wrong and misleading.

> Calorie in calorie out is the flat-earth model of metabolism, trading truth for simplicity

Are you proposing mammals can burn more energy than they consume, just by thinking about it?

Where do you propose that energy comes from?

That would be an extremely bad summary, because both diets that were tested were 9000 calories/week. It's the entire point of the study, and it seems that nobody commenting here even bothered to skim it before "ackshuallying" it.
From the referenced study supplemental documentation on the “fasting” days and non-fasting days. Even the fasting days they allow you to eat 350-550 calories as aforementioned supplements/snacks for a ~9% weight loss and 17% reduction in desire to eat over 8 weeks. Not bad at all if you can manage to do it: 205lbs->184.

Table https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10107279/bin/OB...

Doc https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10107279/bin/OB...

#15 study https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10107279/#oby23...

Title is misleading, the intermittent fasting this paper is talking about is a brutal 350-550 calories per day restriction. That's just fasting.
Was confused by this, as well. It appears they skilled the intermittent part entirely.
There are 140 calories in a can of coke. All a person has to do is stop drinking two cans a day and make zero other changes and they’ve about met your 300 calorie reduction.

Hardly sounds like fasting to me.

No, you got it backwards. They were restricted to a few hundred calories per day.
ah, sorry, I read that wrong
That's starvation, not fasting.
You don't think they looked up intermittent fasting? The diet was 5-6 days of eating whatever you want, and 35-60 hrs with the 350-550 calorie restriction. It's not brutal, it's standard.

I did M-W-F 400kcal days when I would intermittent fast, for 6 months straight, 3-4 times over about 6 years, and the last time my weight never went up again. I've been years in a 5lb range around my perfect high school weight with no effort or thought, and I completely blame IF.

edit: they buried it pretty good in the paper, but was it really worth commenting about if it wasn't worth checking?

yes, the original commenter doesn't know what he's talking about. 35 hr is low end of IF. I did it on a whim with 0 calorie intake (water only), my colleague done it too.

I didn't even know that with 500 calories per day (it's like a whole bagel with cheese) you can still call it "IF", sounds cheaty.

I'm actually more interested in side effects of prolonged IF or fasting in general. My impression over the long term is it can contribute to gastritis. I don't see any evidence to support this other than anecdotally how it feels to me.
NY Post: "Mysterious alien eggs spotted in Oklahoma lake"

NY Post: "Trump tells Dr. Phil evil forces are controlling Biden"

NY Post: "How intermittent fasting, protein pacing can lead to weight loss"

What could go wrong?

Just waiting for alien abduction and Elvis being alive and well articles to come out and we've got a new version of the old National Enquirer.
Not only can basically everything you do lead to weight loss in some way, if your study is "27 women and 14 men", it might just be impossible to draw any real conclusions about population wide effects from it.
> Despite similar average weekly energy intake (~9000 kcals/week) and physical activity energy expenditure (~350kcals/day; p = 0.260) during the intervention, participants following the IF-P regimen lost significantly more body weight (−8.81 ± 0.71% vs.−5.40 ± 0.67%; p = 0.003; Fig. 1c; Supplementary Data 1) and total, abdominal, and visceral fat mass and increased fat-free mass percentage (~2×; p ≤ 0.030), as previously reported.

Interesting. Calorie in, calorie out getting btfo'd lol. I'm guessing the gut microbiome change has a lot to do with this, not just the fact that the body is forced to use more protein.

> The IF-P regimen consisted of 35% carbohydrate, 30% fat, and 35% protein for five to six days per week and a weekly extended modified fasting period (36–60 h) consisting of 350–550 kcals per day using randomization, as detailed previously. In comparison, the CR regimen consisted of 41% carbohydrate, 38% fat, and 21% protein in accordance with current US dietary recommendations

Wonder if the fat loss is due to intermittent fasting or the higher protein. Guessing a combination.

Also should note that the IF-P diet has "significantly" less sugar and more dietary fiber than the CR diet, which would also contribute to the gut microbiome change and the fat loss etc.

There’s also likely an element of plain old inefficiency associated with throwing a bunch of food in the body at once. Every protein, fat, carb broken down has to be done so by some physical/chemical/enzymatic action.

There are only so many chemical/enzymes in the body. If you put a small amount of food in, it’s more likely all of it will be completely broken down more effectively. If you try to digest a larger amount of food in at once, it seems plausible the digestion process could be less efficient.

Good point. Another thing is the participants might not finish the relatively large high protein meals that IF-P would have compared to the smaller CR meals.
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The core principle is still calorie restriction, this is just a modifier on top of that.

If they ran it with 18k cal per week then both would gain.

I don't think anyone thinks that macro/micronutrients and eating patterns are completely irrelevant, just that they have less effect than total calories, so IIFYM is a good starting point / first order simplification.

The core principle is still calorie restriction, this is just a modifier on top of that.

If they ran it with 18k cal per week then both would gain.

I don't think anyone thinks that macro/micronutrients and eating patterns are completely irrelevant, just that they have less effect than total calories, so IIFYM is a good starting point.

I would draw an analogy with say, distance running training. My understanding is that it is generally agreed that total mileage run is (within reason) the most important variable, and after that you have things like speed, intervals, other training, etc.