Sunny at Healthy Girl brings up the role of genetics in eating disorders. I tend to have an irrational gut reaction against thinking that my issues could stem from a brain-wiring issue; I prefer to think that my problems stem from some sort of murky thing that happened circa 1979 or so and can be unearthed through therapy alone (which is why I was in therapy for 7 years before I quit). But it's obviously a worthy question.
One sort of offshoot question about genetics and eating disorders, though: What did people with ED genes do before eating disorders were, well, "invented"? I mean, I know that eating disorders go way back--Freud writes of patients with symptoms we now term anorexia, for example. But EDs have become a sort of handy place for people with generalized "issues" to turn. The "hysteria" epidemic of the 19th century wasn't actually an epidemic; rather, it was a way for culturally restricted women to act out in a way that, though it wasn't exactly understood by the establishment, was at least recognized. In the same way, EDs are far from understood in our culture, but we recognize them as requiring care.
It makes sense that there's a good amount of ED sufferers out there who turned to restricting or bingeing or purging not because some synapse organically told them to, but because in a culture that A) has an abundance of food and B) therefore treats food not as nutrition but as a thing of cultural and familial significance, and C) has a strict standard of beauty that requires thinness, food seemed like a pretty good way to deal with personal issues. In much the same way that hysteria became nearly a fad in the 19th century--not because it was to be aspired to, but because it was a recognizable funnel for one's social and personal issues--eating disorders can spread like wildfire in our environment.
What the studies linking genes with eating disorders are actually saying isn't exactly that there's a gene that makes you want to starve. ED sufferers are more prone to irregularities in mood-regulation hormones--the same hormones that play a role in depression and anxiety. And one way to spike a low serotonin level (linked to depression) is to eat lots of sugar (a common binge target); similarly, a way to calm a perpetually high serotonin level (linked to anxiety) is to starve it to death. But plenty of people have messed-up hormone levels--some just deal with it, others go on medication, others self-medicate through addictive substances or behaviors. Not all of those people go on to develop eating disorders.
And that's where images come into play for people who develop not just unhealthy body image, but eating disorders. When your mood regulators aren't regulating themselves and you find something that "works" for you (e.g. bingeing or restricting), you do that thing. And you have reinforcement on every billboard and magazine cover around you.
It's much more complicated than what I'm saying here, and it varies patient by patient. Few people in the ED community would argue that EDs are caused exclusively by genes, brain chemistry, family, or culture. The combustion point of all these factors (and more) is where EDs spring from. I'm just wary of jumping too heavily on the "it's genetic" bandwagon. If the "it's in the genes" theory comes to dominate ED research, it's not too far-fetched to think that ED treatment can be written from a general practitioner's prescription pad instead of from the comprehensive therapy that currently comprises ED treatment. (Which is the case with several other psychiatric and mood disorders.) And if an ED sufferer opts not to swallow a pill, then what are they complaining about? There's a "cure," after all. And then we're still left with the cultural images that tell overweight women that they're not really worthy; images that exclude an enormous proportion of beautiful people. We're left with associations with the words "thin" and "fat" that have nothing to do with being thin or being fat (like pretty, or slovenly, or loved). We're left where we are. A pill might be nice for ED patients, but it'll suck for everyone else.