It’s pretty clear to me, Fung is wrong.
I never could wrap my mind around this thinking… Zillions of people loses fat by eating less, it’s even logical if someone’s body works in a certain way. It always very nicely works for my family members, including me. I just can’t eat little so under a certain energy need, I stuck.
I understand not everyone is this “simple” but it’s always CICO, just the complicated one where CO is a complete, CI is a partial mystery. But some people can guess it pretty well because they are “stable” enough or not sensitive to various things. Or their body doesn’t believe it’s famine if the food is a tad less. So they can use the simple but in general clearly wrong CICO too.
Other people may find their own way. I need some tricks myself.
A huge extra energy intake for a long time may result in no or tiny gain due to genetics (I have lots of personal experience). Sometimes the metabolism quickens quickly and very much. I’ve read it’s not even very rare but somewhat unusual, yes. So that part is individual too.
I have no knowledge, personal experience with metabolism slowing but some people loses fat at a quick, almost stable pace for long when starving too. It’s probably very complex but I would think their metabolism doesn’t “like” to slow down too much or too soon. Probably the energy need matters too, it’s problematic to have a huge energy deficit if one needs very little energy to begin with. Starving at 200 kcal and starving at 1300 kcal is probably quite different and the reserves of the body are there too… Way too individual.
Fasting. If “works” mean it causes fat-loss, well, it clearly doesn’t work for me (except under special circumstances. A 5 minutes long eating window would have a very good chance, for example. 30 minutes is dubious, it depends on my diet, probably). It worked only when I ate little enough calories but that worked anyway, I never noticed a difference (but I always was very close to 16/8 and it’s just me, with my body surprisingly insensitive to many factors).
It automatically works for many, of course and some people can’t not starving on IF so it works “too well” for them.
I believe there is some extra help due to hormones and other things. It makes fat-loss easier for many. But calories are heavily involved, at least almost always. And some of us never have a noticeable bonus anyway. We just eat less and get satiated better and for longer easier - or not. IF isn’t for everyone.
I heard many stories and IF clearly reduced calories in most cases. Many intermittent fasters (especially beginners who aren’t used to “big” meals yet) often eat quite little, not even enough for a healthy fat-loss. Others eat at an okay amount but still less than their needs.
And the OMADers who eat 4000 kcal in one sitting because they are that hungry, they usually don’t lose fat at all even if they have fat to lose. It’s not magic, working for everyone, no matter what.
I only lost fat on OMAD when I went below my usual energy need (it’s quite stable in the last several years) though my experience is little, I usually do 19/5 with low-carb/keto. I inevitably gain fat on a carby IF if I eat at least twice every day, that’s serious enough overeating even with my genetics.
We are very, very different. Let’s keep that mind. I accept some people function in interesting ways compared to me but they shouldn’t say something works for everyone, no matter what when many of us experienced that it’s not true, even when we did it way stricter and put effort into it, for a very long time.
I focused on the cases similar to mine, of course there are explanations for the ones who have some bonus on IF. Even my body probably does those things just not to a noticeable extent. I just wanted to say it’s clearly not huge for everyone and it’s definitely not the reason why fasting “works” for so many.