Mostly I think it's the fault of the media. They keep telling/showing us that skinny is beautiful. That we should buy their products in order to look like the people who THEY say embodies perfection.

In older days, in many cultures, men liked chubbier girls because that meant that they were rich enough to be able to eat in excess.

Even when you look at statues from classical Greece, the women weren't sculpted "toned and skinny", they were curvy, and beautiful.

I'm not condoning obesity, by the way. There is a limit... anything after that limit is just not healthy.