@goldenmist - You make a decent point, but I also think it’s important to remember that obesity is a bigger problem in countries like America than thinness. You have to consider natural or genetic metabolism as well; I for one eat what I would consider to be a healthy diet but am still much skinnier than the average person. I've seen doctors and they've told me not to worry about it.
And unhealthy eating practices don't just result in thinness, either. If you haven't eaten in days then you might be skinny, but you're probably not going to look very attractive. Diet affects your complexion and overall health and without that you’re not going to look like a model, so there’s no point starving yourself.
Probably the best course of action is to prevent girls from comparing themselves to models in the first place. Models are not average at all, that's why they're models. They're naturally thin, have high cheekbones, eyes set far apart, etc. It's just like how you shouldn't compare your life to a movie.