Is a need for skinny jeans in the genes?

New evidence finds that anorexia may be at least partly genetic.

By Carol Lloyd

Published December 6, 2007 10:00PM (EST)

Now I know why my thin and lanky husband sometimes lingers in front of the mirror, studying his well-defined rib cage and complaining that he's fat. He has a twin sister, that's why!

If this sounds like I'm suffering from end-of-the-year non sequitur, read on. While women suffer from anorexia at 10 times the rate of men, one recent study found that some men share about the same risk as women. According to a new study published in the December issue of Archives of General Psychiatry, men who have a twin sister are more prone to anorexia nervosa than other guys. In fact, they are almost as likely to develop anorexia as females.

There's no conclusive evidence as to what causes this. But researchers, who analyzed data from a study of Swedish twins born between 1935 and 1958, guess that exposure to female sex hormones in utero may raise men's risk. "A plausible explanation for this phenomenon is that in pregnancies bearing a female fetus, a substance is produced, probably hormonal, that increases the risk of having anorexia nervosa in adulthood," the study's authors wrote in a press release. "The most likely candidates are sex steroid hormones."

This study may cast some light on my husband's mild body dysmorphia. (He's far from anorexic, but he exhibits more distorted body image than your average dude.) But it completely muddles my understanding of anorexia nervosa as a cultural disease. In countries where zaftig women get the most mojo, are there still (owing to these biological factors) a certain number of people who want to starve themselves?

A brief search on the causes of anorexia only made one thing clear: The jury is still out. According to WebMD, the cause of anorexia nervosa is "not fully understood" but might develop in response to "physical, emotional, and social triggers" including genetics, dieting, stress and personality traits like perfectionism. The National Association of Mental Illness Web site devotes more space to cultural and psychological factors. Along with mentioning that the illness runs in families, the NAMI Web site notes that "obsessive dieting behavior reflects today's societal pressure to be thin, which is seen in advertising and the media. Others especially at risk for eating disorders include athletes, actors, dancers, models, and TV personalities for whom thinness has become a professional requirement."

But the evidence that anorexia has deep physiological causes is mounting, and for parents of girls struggling with it, it's probably a relief to hear that it's not all their fault. Last year, another study found that anorexia was largely a heritable disorder rather than a pathological response to fashion tyranny. Still, it would be interesting to see some cross-cultural studies in countries where fat is truly phat.

Carol Lloyd

Carol Lloyd is currently at work on a book about the gentrification wars in San Francisco's Mission District.

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