Many mysteries unsolved in binge-eating disorder

It is likely that binge-eating disorder (BED) will be included as a psychiatric diagnosis in DSM-5, Timothy Walsh, M.D., said at an April workshop on the topic at the Uniformed Services University of the Health Sciences in Bethesda, Md.

Walsh is a professor of pediatric psychopharmacology at Columbia University/New York State Psychiatric Institute and chair of the Feeding and Eating Disorders Work Group for DSM-5.

“One reason that I believe BED is going to make it into DSM-5 is because sufficient research has been conducted on it,” Walsh explained. As he told Psychiatric News earlier this year, “In the 20 years since publication of DSM-IV, there have been more than 1,000 papers published on BED” (Psychiatric News, January 6).

Nonetheless, many questions about the disorder press for answers, Walsh and other workshop speakers concurred.

For example, one gene, called FTO, which is expressed in the hypothalamus, has been linked with BED, Marian Tanofsky-Kraff, Ph.D., an associate professor of medical and clinical psychology at the Uniformed Services University, reported. But are other genes involved as well? Researchers don’t know.

While maltreatment, teasing, and bullying have been identified as BED risk factors, other childhood risk factors for BED also need to be identified, Cynthia Bulik, Ph.D., director of the eating disorders program at the University of North Carolina, stressed.

Chevese Turner, founder and chief executive officer of the Binge Eating Disorder Association, related that when she was a little girl, her mother had anorexia nervosa and talked a lot about dieting. Both factors encouraged Turner to start binge eating, she believes, and she started doing so as early as at age 5. Yet BED is usually uncommon before adolescence, Tanofsky-Kraff said. Why is this? Researchers don’t have the answer.

A major criterion for BED is loss of control over eating. Yet how does the mechanism of loss of control in BED compare with that of the loss of control in alcoholism or drug abuse? Stephen Wonderlich, Ph.D., associate chair of clinical neuroscience at the University of North Dakota, asked. “And there is not yet enough research to determine whether binging in BED is the same or different from binging in bulimia nervosa,” Walsh noted. “We also need to determine the relationship of loss of control to amount consumed,” he added. “Our knowledge of how these pieces fit together isn’t as good as it could be.”

Although there is a strong cross-sectional relationship between BED and obesity, there have been few longitudinal studies to see whether BED causes excessive weight gain and obesity, Alison Field, Sc.D., an associate professor of pediatrics at Harvard Medical School, said.

Even if binge eating can lead to obesity, why don’t all binge eaters become obese? Mary Boggiano, Ph.D., an associate professor of psychology at the University of Alabama, asked that question after she and her colleagues conducted a binge-eating study in rats that found that not all binging rats became obese.

The experts are also wondering how grazing and night eating fit into the BED picture. “I don’t think there is much data about grazing,” Walsh commented. “There has been some research about night eating, but the definition does not seem to be stable. This doesn’t mean that they don’t exist, but there is insufficient data to recognize them formally in DSM-5 as disorders.”

As for treatment for BED, better options are needed, workshop speakers pointed out. Specifically, ample research has demonstrated that cognitive-behavioral therapy and interpersonal therapy can counter binge eating and lead to long-term weight loss, reported Denise Wilfley, Ph.D., a professor of psychiatry at Washington University. Yet the amount of weight lost with these two therapies is modest, she said. And while there is one drug on the market that has shown good efficacy against BED—the anticonvulsant topiramate—it can have undesirable cognitive side effects, noted James Hudson, M.D., Sc.D., a professor of psychiatry at Harvard Medical School.

Walsh asked Hudson what he thought about using topiramate and the appetite suppressant phentermine together to treat BED. Hudson replied: if the combination is approved by the Food and Drug Administration as a treatment for it, undoubtedly it will be widely used.

Source: American Psychiatric Association