Reply #22: I think that it is both genetics and environment

[Nikia]

It seems everything reienforces itself. Recovering from anorexia, I try to make sense of all this. The less that I ate and less frequent that I ate, the less that I wanted to eat. When I feel stress, I don't want to eat. I think that these tendencies are stronger in some individuals than others.
The negative self talk comes from somewhere though. If it were considered good to be overweight, we wouldn't be having negative thoughts about having some fat on our bodies. If it were a positive thing to eat large amounts of food, we wouldn't think negative thoughts about eating too much.
Instead every person exposed to normal media hears things like this: (parentes are how my mind has twisted it) "Fat bad." "Thin good." (One can never be too thin.) "Americans are too fat" (I'm an American, therefore I must be too fat.) "It is bad to eat a lot of fat and carbohydrates." (It must be even better not to eat any fat and/or carbohydrates.)
I am in an eating disorder support group. Everyone of those women is a perfectionist, usually a fallen perfectionist, and cares or has cared more about others needs than her own. Almost all of us have some type of anxiety disorder too. Perhaps this is related to the genetics of it (Anorexia could have been an adaptation to feed ones children, who were less able to survive, in times of famine by going without food oneself.), but I think that a lot of this is an expression of stress and feelings. We want to be perfect, but have been unable to be perfect at the things that we wanted to be perfect at so we seek to be perfect at something that we seem to have a naturual talent at. We feel that others, important people in our lives, will not accept us if we are not perfect so we become perfect in the way that we can, either quite innocently or even vengfully "Maybe, you don't really want me to be perfect, do you?" . Feeling that others are more important or that you are expected to defer to others can be expressed as an eating disorder too. "I am not important enough to waste food on." "I want to take up as little space as posssible or even just disappear so that I don't hurt or inconvience anyone." "I don't need anything at all." or the vengeful reverse psychology "You won't let me meet my needs. I won't meet my need for food. I'll show you what happens when my needs aren't met."
I do think culture is responsible in that thin=good and that there actually seems to be more black/white thinking. None of the women in my eating disorder support group are what I'd term "glamour girls" though. Some probably are, but probably even less than in the general population.
As for thoughts why it might be appearing at a younger age, it could be environmental. Children are picking up on the thin=good message at younger ages and are exposed to it more often. They are dieting as a group at younger ages, including many who never develop eating disorders. Children also seem to be under more pressure for success, of all types, than they were in the past. Biologically, children go through puberty at earlier ages and this disease might be related to that change in many young people.