Funny that you mention it, because I do have a punch-line that I tell obese people - it goes like this: "Eat little, fuck a lot". This is really just Occam's razor. Most people would feel better, if they would eat thoughtfully and do physically activities that they enjoy.

btw.: I was the fattest, weakest kid in high-school and after a decade of hard workouts and a strict diet, I can probably beat up most other guys and I also look better.