I also noticed the same in many people, as well as myself. And I do not think the other commenters are correct in their explanations. At least in myself, I can

I also noticed the same in many people, as well as myself. And I do not think the other commenters are correct in their explanations. At least in myself, I can clearly see that in my 20s I had a much more sedentary lifestyle, sitting in front of a computer a heck of a lot more, having less social life and eating _much_ worse (processes food, sweets, coke) and still being able to maintain a normal BMI. If its not metabolism it must be some other mechanisms that allows people to do it, but metabolism seems the simplest one.