Credit: malias
I devoted April to blogging about fitness and nutrition, which meant that I spent a lot of time on dieting websites. There, dieters could find support, encouragement, and advice as they tried to shed unwanted weight and live a healthier lifestyle. The people on these sites (mostly women) were almost universally enthusiastic and positive about the changes they were making in their lives.
Occasionally, though, I encountered a different sort of person: Insecure, anxious about her appearance, concerned more about herself than what she could give to others. Other forum members noticed the difference too, and would try to direct these women to psychologists to get help: They were showing signs of an eating disorder. While obesity can kill, anorexia nervosa and other eating disorders can kill much faster.
A 2007 study found that nearly 6 percent of women and 3 percent of the men in the US suffered from some type of eating disorder during their lives. Of the three major eating disorders (anorexia nervosa, bulimia nervosa, and binge-eating disorder), anorexia is the deadliest, and fortunately, also the rarest. But it still affects 0.9 percent of women and 0.3 percent of men—a higher incidence rate in women than brain or cervical cancer. Even during the so-called obesity epidemic of recent decades, anorexia rates showed no signs of decline.
People with anorexia essentially starve themselves. This usually means they simply refuse to eat, but they can resort to almost any method to lose weight: excessive exercise, inducing vomiting, or abusing laxatives or diuretics. The underlying causes of anorexia, however, are elusive.
One clue may come from brain activity of anorexics. “Scicurious,” a neuroscientist who blogs at Neurotopia, took a look last week at a 2005 study on brain differences in recovered anorexics and bulimics.
The researchers, led by Guido Frank, reasoned that since the neurotransmitter dopamine is a key component of addictive behaviors, anorexics might have a different response to dopamine than non-anorexics. The brains of anorexics and bulimics showed an increased response to dopamine than normal brains, but only for receptors that inhibit activity. While the research couldn’t show exactly what activities are inhibited by dopamine, it’s certainly plausible that ordinarily pleasurable activities such as eating might be among them. Dopamine can be produced by the brain when a person is given positive reinforcement (“April, you are looking thinner every day!”), which in anorexics might then inhibit eating, which leads to further reinforcement. The research was published in Biological Psychiatry.
While dopamine and dopamine receptors may play a role in anorexia, in March the Dutch psychiatrist Walter van den Broeck, who blogs as “Dr. Shock,” pointed to some preliminary findings suggesting another potential cause. Normally, people are able to update their opinions of themselves based on external feedback—compliments, photos, images in the mirror. But some research suggests that the medial temporal lobe of the brain, involved in integrating self-image with the image others have of an individual, may be impaired in anorexics. The article cites research showing that this region can actually be damaged by recurring stressful events, even including teasing by peers or pressure from coaches. With impaired function of the medial temporal lobe, anorexics are unable to update their body image, and so even as their bodies waste away, they still see themselves as “fat.”
Another piece to the puzzle of anorexia comes from behavioral research. Oklahoma physician Bill Yates discussed one study of set-shifting ability in women with eating disorders. Set shifting measures how readily people adapt to changing tasks. Participants in set-shifting studies might be asked to sort playing cards according to suit, then halfway through the test switch to sorting by rank. In the study, women with eating disorders performed significantly worse on such tests than healthy women. Interestingly, the particular disorder didn’t matter. Body mass index (BMI—a measure of thinness) also didn’t correlate to performance on the test. Bulimics with healthy BMIs performed just as poorly as underweight anorexics. The research was published in the Journal of Psychiatric Research.
Training in set-shifting is now a common therapy for eating disorders. Some therapists have found that training women to become more generally adaptable is a first step in changing entrenched beliefs about healthy eating and body image.
Despite these advances, the problem shows no signs of abating. The 2007 study found that most women don’t seek treatment for eating disorders. This may also mean that the true scale of the problem is underestimated.
As we learn more about anorexia and other eating disorders, look for the latest news on ResearchBlogging.org.
Dave Munger is editor of ResearchBlogging.org. He also blogs at The Daily Monthly. Each week, he writes about recent posts on peer-reviewed research from across the blogosphere. See previous Research Blogging columns »
Originally published May 5, 2010
