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Taste in the Brain

The brains of women who suffer from anorexia nervosa may actually respond to taste differently, according to research published in the journal Neuropsychopharmacology. The report suggests that women with anorexia might not experience the rewards from eating that non-anorexics do.

Psychiatrist Walter Kaye, who led the study, says the findings may explain how people with anorexia are able to starve themselves, sometimes to the point of death. “Food may not be as rewarding as it is to people without an eating disorder,” Kaye says. “And this may very well explain why they’re able to not eat, and lose so much weight.”

He says the brains of anorexics may not be producing “a very robust signal driving eating behavior,” even when the body needs food.

Karen Pearlman, a sports journalist who struggled with anorexia during her teenage years, recalls “not really caring about” what she ate. “Just the least amount possible,” she says. One winter, Pearlman dropped from 120 to 85 pounds. In the spring, when warmer weather meant shorts and t-shirts, Pearlman’s parents saw how thin their daughter had become, and they took her to get help.

Now 41 years old, Pearlman reports a full recovery, but she says it took time. She was still dealing with body image issues into her twenties. “It becomes so, like part of who you are. It’s very hard to let that go,” she explains.

According to Kaye, although over half of anorexics do recover, people usually suffer with the condition for between three and ten years. “That’s a very long time to be ill,” says Kaye.

Affecting between .5 and one percent of adolescent women in the United States, anorexia nervosa includes symptoms such as anxiety, obsession with weight, and disordered eating, according to the U.S. Department of Health and Human Services. And although recovery is likely, the condition is lethal in one of every ten afflicted women.

Kaye, who has worked with anorexics for 30 years, describes the condition as “a very puzzling disorder. We haven’t understood issues like food restriction or weight loss or body image distortion, and it’s very hard to come up with more effective treatments until you understand the underlying physiology that may be contributing to some of the symptoms.” He says he began this study to answer the question, “Do people with anorexia not get the same message that other people do when you get hungry?”

To conduct their study, Kaye and colleagues from the University of Pittsburgh and the University of California, San Diego, examined activity in the brains of 16 formerly anorexic women and 16 control subjects. Using functional magnetic resonance imaging, or fMRI, the scientists compared activity in various brain regions of the volunteers as they drank sugar water and regular water.

While sipping sugar water activated a brain region called the insula in control subjects, the same pleasant sweet sips stimulated less activity in that region in recovered anorexics. Previous studies have established that the insula plays a role in both tasting food and experiencing rewards from eating.

But do the brain differences cause the eating disorder, or are they a result of it? Kaye says this study could not answer that question because the research only focused on recovered anorexics. The reason for studying recovered anorexics was that malnutrition may alter the brain scans of people actively struggling with anorexia. But he says future research may provide answers.

The controlled study specified that subjects had to be fully recovered from anorexia, with stable weight, normal eating habits, and regular menstrual cycles for over a year. All of the subjects ate a standardized breakfast of bread with butter and marmalade to make sure that they were all equally hungry when their brains were scanned. Finally, during the actual fMRI scan, the subjects swished the sugar water around in their mouths before swallowing to guarantee they could fully register the sweet flavor.

The fMRI technique detects how much oxygen the brain’s tissues are using. Brain regions that are activated use more oxygen. By comparing the brain scans of former anorexics and control women, Kaye and his associates were able to pinpoint the lessened insula region activity.

According to Kaye, the research may indirectly lead to new treatments for anorexia. “In the long term,” he explains, “it’s very likely to lead to a more effective treatment. Because once we begin to understand the pathways that may be contributing to these kinds of symptoms, then we can understand much more about the biology of this.”

One constraint of the study was that all the subjects were women. Therefore, researchers do not know if brain activity in men with anorexia matches the pattern Kaye and colleagues uncovered. Although women make up 90 percent of anorexics, the prevalence of eating disorders among men may be increasing.

As for Pearlman, she says she’s glad researchers are a step closer to figuring out what’s behind this condition. “The more research that’s done, people can find out how to help, especially young women, and men too, she says. Pearlman hopes her own recovery will provide hope to people combating anorexia now. “I’m pretty comfortable in my own skin and I have been for some time,” she says.

This research was published online in Neuropsychopharmacology, May 9, 2007 and was funded by the National Institute of Mental Health and the Austrian Science Fund.

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