I have so many girlfriends whose self-image has been completely ruined by the media and society. Eating disorders have many roots and causes, and I see this in the women around me. Obesity, for instance, can easily be either purely medical or purely psychological, or it can be a combination of both.
It's not neccesarily that people lack willpower, and I think a lot of people are too quick to put the blame there. I think it's more that our lifestyles have changed soo much over the years--we do less physical labor, junk food has become cheaper and more easily availible, we have more leisure time. It's harder for us to find activities that challenge our body the way working in the fields all day would. Our desire for more leisure time has led us away from preparing healthful, home-cooked meals. When leisure time comes, we spend a lot of it in front of the television--which, I might add, burns less calories than lying in bed and reading a book or studying.
I think our society is as much to blame as the individual. Look at what they serve in school cafeterias. My typical lunch in high school consisted of a bottle of Coke and a hot dog. The amount of fruits and vegetables availible was a joke, and what was there was disgusting. Obesity is rapidly becoming the problem of society, and not just the person.
However, I would also like to point out that nutritionally, Americans are much better off today than they were even 100 years ago.
One bright spot.