Which study are you referring to? He references different studies to make different points and I can’t tell which one you’re talking about.
This one, mentioned in this context:
> This was a randomized crossover, isocaloric and eucaloric study. That is, all patients did both arms of the study eating the same foods and the same calories and then compared against themselves. The two arms of the study were eating between 8am and 8pm, and the eTRF strategy of eating between 8am and 2pm, but remember, both groups ate three meals per day of the same foods. Some would start with the conventional diet, then cross over to eTRF, and others did the opposite, separated by a seven-week washout period. Subjects were men with prediabetes.
> The benefits were huge. Mean insulin levels dropped significantly, and insulin resistance dropped as well. Insulin is a driver of obesity, so merely changing the meal timing and restricting the number of hours you ate, and also by moving to an earlier eating schedule, produced huge benefits even in the same person eating the same meals. That’s astounding. Even more remarkable was that even after the washout period of seven weeks, the eTRF group maintained lower insulin levels at baseline. The benefits were maintained even after stopping the time restriction. Blood pressure dropped as well.
Specifically this sentence:
> so merely changing the meal timing and restricting the number of hours you ate, and also by moving to an earlier eating schedule, produced huge benefits even in the same person eating the same meals
is incorrect, and is basically the lynchpin of the entire IF idea.
Maybe you meant to question the study itself, but I don’t understand your objection to that either. The study tests whether this form of IF improves certain markers of metabolic health, and it shows it does — within the design of the study, of course, but that’s true of every study and doesn’t make it meaningless. You seem to be implying it doesn’t work in the way IF proponents think it does. That may be true, but isn’t relevant to this study since it doesn’t attempt to answer.
The study, like all similar IF studies, showed that people who do IF sometimes are able to use it to consume fewer calories. That is important from a compliance standpoint: it means you can use this diet to treat obesity for some portion of the population for whom it is going to be effective because it will get them to comply with not eating too much. Not eating as much is associated with weight loss which is associated with all kinds of good outcomes. That's awesome, but it doesn't mean that metabolically there is something significantly different going on outside of eating less.
This is an important discussion in nutrition in general, and shows up in IF as well as keto discussion frequently, with proponents of each arguing that beyond the compliance aspect, there is also something special going on with your metabolism (ie: insulin sensitivity and other metabolic markers). The problem is that all of these are things that improve when you are in a caloric defecit, and the studies never disambiguate between the effects of a caloric deficit and the meal timing itself.
Fung makes the same mistake the authors of the paper do in interpreting their own results too optimistically. The dietary controls are set up in a way to make it seem convincing in an abstract if you are familiar with this area and what the current core issues are, but it is not at all if you dig in.