Can you cite a source? Hell, I'll lower the bar, can you even explain the logic in that?
First time I've ever heard someone try to make the link between ambition and excess weight.
I know tons of overweight highly successful individuals, in fact some of the most successful people I know are overweight, they simply work all hours of the day and eat crap between work.
It is an unhealthy lifestyle, absolutely, but an indicator for a lack of ambition? ...
This is a fucked up world view. The underlying assumption seems to be that every human has the exact same metabolism, hence if you're lean and fit you have willpower, self-discipline, and self-control, and if you're fat you don't because you've 'let yourself go'.
But by that measure everyone who isn't an Olympic athlete lacks a certain level of willpower, self-discipline, and self-control as well, since that's the only differential between Olympians and non-olympians.
Bodies are different, metabolisms are different, and each person has a natural equilibrium state. For some people that equilibrium state is lean and skinny, and it takes relatively little willpower or 'ambition' to maintain it. In fact, some can't even get overweight if they try.
For others, their equilibrium state is to be overweight, and it takes a relatively herculean, constant, unending effort to reach and maintain the former's same level of leanness.
Food also affects different people in different ways. It's no secret Americans have gotten fatter in recent decades, and one of the main culprits is our increasingly poor diet. But even there, some people are more resistant to gaining weight from poor quality food and/or overeating while others have to stick to a strict diet, count every calorie, and work their ass off in the gym just to look like the former does without even trying.
We seem to be getting better at hacking our metabolism lately, judging by what I've read of Paleo/Primal, stuff on Lifehacker, etc. I wonder if anyone has ever applied to YC by answering the application question "what was your best hack?" by saying they were naturally obese and hacked their body/metabolism to overcome it. It's not easy.
You are right! But consider that many thin people make a huge effort to be that way and with that comes resentment that they are foregoing all the nice things (chocolate, beer, snacks, etc) I hate group dining where one person is a diet & exercise Nazi - really spoils the atmosphere. Pass the chocolate mousse and cognac!