The common theme in normal weight individuals is their comparative lack of food drive, not an outsized capacity for willpower. When you talk to "skinny" people

The common theme in normal weight individuals is their comparative lack of food drive, not an outsized capacity for willpower. When you talk to "skinny" people you'll hear things like they just forgot to eat or I just had a couple bites of cake then felt full/had enough. Alternatively when you speak with heavier people you'll realize that they're white knuckling their entire lives (because calories are so abundant). On average they're actually exerting more willpower around food than skinnier people. Not everyone of course, there are folks in either camp, but at population scale lack of food drive is what keeps people skinny in a calorie rich, low activity environment.