(...) it's not even about eating less  Weeeell now. You're awfully close to HAES logic there, buddy.  It is everything to do with eating less. It's all about calories in vs calories out. If you eat fewer calories than you use, you will lose weight. In other words: you can be slim and eat two hamburgers a day (about 750kcal each). It may not be the most healthy thing you can do, since most burgers contain lots of sugar and salt, but you will lose weight if that's all you eat (and you have a base burn of more than 1800kcal per day).