Anybody remember when Taubes said something about delta V? When the system gets bigger, Eout increases, Ein must increase to compensate. If Ein stays the same, Eout must decrease to compensate. Well, those fat lumps is exactly that, the system got bigger. So, after 40 years of eating carbs and growing bigger fat tissue, we gotta eat more to feed that increase. Or, we grow more lethargic because we don't eat more.

The point is that the system got bigger and caloric intake had nothing to do with it, and has nothing to do with making the system smaller now.