Plus-sized models have had quite a bit of publicity as of late, and are generally applauded for their role in propping up the self-esteem of the vast majority of human females who do not have the genetic specifications dictated by the fashion industry and popular media in general. Except, recent studies show that their actual effect on women's psyches isn't very positive either. Via The Frisky:

According to the researchers, larger women feel better about themselves when ads don’t include any models at all, average-sized ladies actually have lower self-esteem after looking at ads with plus-sized models rather than uber-skinny ones, and thin folk prefer the traditional tiny models. The study did, however, come up with one icky way bigger models can be used to actually influence product sales: ” ... if a normal-size woman sees moderately heavy images in ads for weight-loss products, she might feel overweight and be more inclined to buy a diet plan or gym membership.” This is basically saying ads could use plus-sized models to make women feel bad enough about themselves that they want to spend more money on gym memberships and diet products.

I agree that it doesn't matter what size a beautiful woman is. If someone looks great (and to most people that doesn't necessitate "size 0" status), and you have crappy self-esteem, that's going to exacerbate it. What we should focus on is turning those feelings into motivation. Gym memberships aren't such a bad idea.