The media have a big influence especially on young girls, they see digital modifications of models and think that is what guys like and what they should look like. But from my experience boys and men don't like really skinny girls and women.
I have alot of friends whom, when they look in the mirror, they lift their shirts/tops w/e and complain for ages about how fat they are, even when they have a fine figure.
I'm the only one out of my friends who don't complain :\ I eat loadz and loadz but I do quite alot excersise and simple stuff to keep toned. I do alot of boxersise. But its not just as simple as excersising to a person suffering from anorexia as it's a state of mind. I don't care about putting on weight and personally I think really skinny people look pathetic. There heads are always too big for their body.
I think its a real shame that this happens to people