Well, I AM a medical professional, and there is a significant factor here that none of you guys has addresed...
A large majority of the overweight people I care for in the hospital simply don't give a flying poop! I had a 34 year old guy admit to me once that he knew he shouldn't have allowed his BP to stay at 220/130 for ten years, but he didn't like the fact that BP meds made it more difficult for him to get an erection. Guess what? Now he's in chronic renal failure and will be on dialysis 3x per week the rest of his life.
It's the same with fat people....most of them just don't care enough about the consequences to do anything about their problem. You see the same thing with smokers. We're required to at least offer smoking cessation teaching to all smokers we admit to our floor, and if I had a dime for how many times I heard "eh, we're all gonna die of something!", I'd be a rich man.
Whenever it comes to making improvements in our health, it all starts with the proper motivation. If it's not there, it just ain't happening.