UPF's in as much as they affect health and obesity rates are almost certainly just doing some combination of the following: People eating more calories because

UPF's in as much as they affect health and obesity rates are almost certainly just doing some combination of the following: People eating more calories because it's more calorie dense / easier to digest/eat People eating more because of things like umami (has no protein but seems like it might be protein) High GI foods causing blood sugar spikes Weird E-numbery ingredients that aren't well studied (e.g. are sweeteners actually healthy for human consumption as opposed to simply not causing acute issues) General lack of nutrition (e.g. if you live on bread and meat with no vegetables things gon get bad) etc. There seems to be a huge aversion in mainstream society to accepting the basic fact that calories in calories out works. It's used by millions and millions of athletes to hit weight classifications, to bulk and add muscle, to cut and reduce body fat, etc. It's about as proven as gravity. You cannot be fat as an average height person if you eat 2000 calories a day consistently. I really doubt that there is any magic here - based on the experience of everyone I know, the thin and fit people eat a certain diet and do certain exercises, the thin and semi-fat (e.g. powerlifter type) people eat a different diet and do certain exercises, and the fat people eat, well, they eat shit, they do not consciously think about what they are eating, in the same way that a well earning person living paycheck to paycheck doesn't have a budget.