1. People in societies where starvation is a serious problem do not have bulimia or anorexia.In my mind, these problems all go together. The common theme is that when humans are not facing any real dangers, they create deadly dangers for themselves, somehow. When outwardly imposed starvation is not a threat, we impose starvation on ourselves through tortured psyches. When death from the outer world is not a threat, we kill ourselves. We need danger, hostility, opposition, struggle. When the world immediately around us doesn't force those things into our lives, we dig them up from our hearts or create them with our culture or bring them into being through our own technology and carelessness.
2. People in environments where there are a lot of deadly diseases don't have deadly allergies.
3. People in time periods where they had to struggle just to survive didn't get paralyzed by depression and commit suicide nearly as often as they do in ours.
Obviously, a possible viewpoint is that in those other situations, the people who currently have these unnatural afflictions were weeded out early. Yet another is that those people were around and just not diagnosed. Either of those explanations still leaves the fact that modern Western society is plagued by these issues that do not plague less materially comfortable societies. When the real problems go away, new ones will show up.