That's a more realistic way of putting it, yes, even if I'd say some of your conclusion is a bit harsh. For people who have been dealt shitty cards, that suffering may be disproportionate to the potential gain, and it's hardly fair to them to assume that their obesity is due to laziness. As a more... indirect possibility, I'd also consider chronic fatigue or other "spoon" conditions. (If you're unfamiliar with The Spoon Theory, the TL;DR is that it's a method of explaining/concretizing the constant energy budgeting people with chronic illnesses have to do.) Even if caloric intake can be healthily restricted, for some of these people it'd likely require outside support, which not everyone has access to.