Why do you think some of us are "bottomless pits" when it comes to eating?
I am NOT talking about people who stuff themselves to bursting. I'm just talking about those of us who "eat until satisfied", but still gain weight. It's a slow process, but we absolutely can gain 50-100lbs over the course of a year. The body just keeps storing the extra calories each week.
Why do you think some people have no problem eating the "correct" amount for their activity level and others do not? (My own brother is like this. He never has to think about it. He instinctively knows the "correct" amount of food to eat, even before he was vegan. He's always had a small appetite.)
Is it because these people were raised on junk food and it screwed up their epigenetics (gene expression) somehow? Possibly even in the womb, given what the mother might have been eating.
Or have we stretched our stomachs out? Or the body is just stubborn about giving up the last bit of fat once its been gained and held for so long?
I know if you starve someone down like they're a holocaust victim, or put them thru a military-training regime, ANYONE can become emaciated or muscular. But if you stop that behavior, BOOM! their body quickly goes back to the way it was. Even if they're eating really healthy. The body "remembers" and wants to go back to what it was. It's just that the speed varies on how fast you return to that set weight point. If you eat junk food, you return really, really fast. If you eat healthy, you get there eventually over a period of time. Somehow, the body knows how to subconsciously manipulate you into eating more than you need so that you always gain weight, slowly but surely.