getting a lot of emails about this study; here's my 30000-foot view. I'll update if the final version differs from the pre-print in any meaningful way.
Nutri-Twitter has a love/hate relationship with Dr. Kevin Hall's research studies. Even I've been critical of some in the past. But he's doing the work. Gotta be one of the most productive researchers in this field, attacking the diet wars from a variety of angles.
Small sample size and short duration, but that's the price you pay for an extremely well-designed and controlled study.
Main endpoint was ad lib food intake. Many people have criticized the short duration: 1) two weeks... fine, but to study ad lib food intake? Many of those same people will champion SINGLE MEAL studies, effects of macronutrient-specific meals on food intake during subsequent meals, etc. In that light, 2 weeks is above and beyond the status quo.
All those studies on "hangry" are 1 day long.
2) insulin, appetite, and ad lib food intake PLEASE DON'T SHOOT THE MESSENGER
Tl;dr: low-fat diet decreased food intake and increased fat loss despite no change in hunger/appetite ratings. Sounds like a win, right? Not quite my bag but if you want some ideas, pictures of the meals are published in the pre-print.
Keto significantly reduced insulin and they were eating a lot more. Lower insulin but no change in hunger/appetite ratings.
wait, what? O_o
There are about a million interpretations of the carb/insulin model of obesity and this certainly provides insight into at least one of 'em...
I understand the criticisms, but ketones were quite high, around 2mM.
And ketoadaptation has more to do with physical performance than appetite. I actually ketoadaptation has little or nothing to do with appetite per se. It didn't happen in this study, but when it does happen, it usually occurs sooner than ketoadaptation.
If it's true (I say "if" because the difference in FI was very large and even if there was a 20% measurement error, it's not sustainable), I think it would normalize rather soon. That's a guess because cutting 600 kcals is gonna leave a mark.
And if it's true given the short-term nature of the study, I suspect the Full Belly Hypothesis. The diets were controlled for the amount of processed foods; a ketogenic diet is much less voluminous. On the flipside, low-fat is high volume and a full belly tends to reduce food intake... at least in the short-term.
What do you think?
That's all for now!
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