Why do teenagers become anorexic?

Why do teenagers become anorexic? ** They become anorexic because there is so much pressure in the media to become thin and, because they have grown up looking at the same body, (as we all do) they can't see that they are constantly changing. Even when they are so skinny they are almost invisible they still think they are fat. Teenagers are also still developingand their hormones are at their worst so they are almost constanly picking out their worst bits, even if there's nothing wrong with them. It doesn't help that there are so many Size 0 people around the world now that it's almost th only thing that we ever see, and they are promoted as healthy and perfect bodies.