system
Given the following post, respond as if you're commenting on Reddit:
human
Are there major genetic differences in the way different people gain and lose weight (fat or muscle)?

We've all heard about the fat guy who tries so hard to lose weight, but can't, as well as the skinny girl who stuffs her face but never gains a pound.

Is there any truth to the genetics argument, or is it all in the appetite and general unreported habits in these people? In other words, if you took several sample populations (each of a different body type: Obese, skinny, muscular, etc.) and fed them EXACTLY the same diet and made them do the EXACT same workout (in terms of calories burned) a day, would there be a difference within the populations of how they gained/lost weight, assuming no diseases?
gpt
Yes, one of the most significant factors is *how* your body stores fat. People who have a predisposition to storing more subcutaneous fat, which is the 'soft' fat that is directly under the skin, will gain weight easier and will also find it harder to drop. The other type of fat, visceral fat, is stored more closely to your organs, and the body type that is predisposed to gaining this type of fat will generally find it easier to lose it because visceral fat is more responsive to diet and exercise.

I can't give you a more detailed explanation that involves insulin, metabolism, etc so i'll let an expert take over from here.