Also, in an effort to change, people will starve themselves or become seriously ill. As you know, many teenagers try to look like models and sometimes end up with eating disorders. Just remember - we don't even look like that. Those pictures are after two hours of hair and make-up, great lighting and then retouching. In terms of weight, yes.
Some models are super thin.
I work out, try to eat healthy and focus on the positive. In males, it's not to be thin. They want to be muscular and end up taking steroids and lifting weights to look manlier in order to impress women. Women want to prove to themselves that they can be prettier or they can fit into an outfit that's smaller. And sometimes it's just to impress certain people.