> Some average-sized adult males get overweight with just 1300-1700/calories a day due to slow metabolisms or other genetic factors.
I think this is largely a myth. (The 1700 calorie end is vaguely plausible but not the 1300 calorie end). There was a good article posted here a while ago [1] which talked about this.
Now, it isn't necessarily easy to maintain a certain calorie count, in terms of either knowing how much you're eating or actually sticking to it despite hunger pangs. And some foods can help you feel fuller with less, you can have different balance of muscle vs fat at the same weight, etc. In those senses I agree with people who say calories in calories out isn't the whole story. But in the end, thermodynamics always wins.
Quote from the article:
> Starvation Mode is this wacky idea that if you eat too little an amount of calories for an extended period of time your body stops burning fat; in fact, it starts doing the opposite–you start gaining weight ‘even when consuming 800 calories’. Sound familiar?
> So, how much truth is there to this?
> Well, see, Starvation Mode is an odd one. Because, while it’s not entirely correct, it’s not entirely incorrect either.
> The correct part: When you reduce calories, more specifically as you begin to get leaner, there is, in fact, some slowing of metabolic rate.
> The incorrect part: Due to this low-calorie consumption your body decides fuck you and proceeds to enter this phantom zone of otherworldliness where the laws of thermodynamics cease to exist, resulting in no fat loss, or worse, gaining fat on some absurdly low number of calories.
It goes on for quite some time, and it's worth reading, but I'll quote just one more part.
> This British actress was adamant she had a slow metabolism, turned out she was simply misreporting calorie intake.
> When she recorded her food intake via video journal, her intake, according to her, was 1100 calories. When they checked her actual intake (with doubly labelled water) it came to 3000 calories.
> Even when she was keeping a food diary, she misreported by 43%.
[1] https://physiqonomics.com/eating-too-much/ discussed at https://news.ycombinator.com/item?id=31381410