That makes binge eating more widespread than the other two eating disorders, anorexia nervosa and bulimia nervosa.
Anorexia affects nearly 1 percent of women and 0.3 percent of men, the study finds; bulimia affects 1.5 percent of women and 0.5 percent of men.
Yet binge eating disorder isn't currently an official psychiatric diagnosis.
The new finding is likely to change that, say researchers James I. Hudson, M.D., ScD; Harrison Pope Jr., M.D.; and colleagues at Harvard University and McLean Hospital.
"These data suggest that binge eating disorder is common -- more common than the other two eating disorders combined. It is associated with obesity, and it is persistent," Hudson said in a news conference held to announce the findings.
For the study, Hudson and colleagues asked detailed questions about eating in face-to-face interviews from 2001 to 2003, with a nationally representative sample of about 3,000 U.S. adults.
They report their findings in the Feb. 1 issue of Biological Psychiatry.
Binge Eating Disorder Hallmarks: Distress, Loss of Control
No, you don't have binge eating disorder if you mindlessly down a dozen hot wings, a burger, and a big bag of chips during the Super Bowl. That is unhealthy overeating, not an eating disorder.
In binge eating, at least twice a week, at times they don't choose — and despite feelings of distress and disgust — binge eaters uncontrollably gorge themselves on massive quantities of food.
Pope says after interviewing hundreds of people with binge eating disorder that he heard the same kind of story over and over again.
"Once they start, they go over the cliff. Even though they feel guilty and disgusted, they can't shut it off," Pope said at the news conference.
"The typical patient tells me, 'I have a normal dinner, and then at 9 o'clock at night I think, well, I'll go down to the kitchen and eat just a handful of potato chips or a scoop of ice cream. But I just can't stop. I eat all this sweet stuff, then I want something salty, and before I know it, I have finished everything in the kitchen,'" Pope recounts.
Strong Urge to Gorge
Food beckons like an irresistible neon sign to a person with binge eating disorder, says Cynthia M. Bulik, Ph.D., director of the eating disorders program at the University of North Carolina at Chapel Hill. Bulik was not involved in the survey but participated in the news conference.
"A lot of these people will say they are unable to inhibit the urge once the thought of eating comes into their minds," Bulik said.
"They say that food will beckon to them like neon signs. They are unable to inhibit the urge to eat once that neon sign goes on. And there is this sense of distress that occurs when the binge eating occurs," Bulik said.
Genetic Predisposition to Eating Disorder
What causes eating disorders? Some people clearly are at higher risk than others.
There's strong evidence that certain combinations of genes predispose people to anorexia and bulimia.
Many people appear to have a genetic predisposition to binge eating disorder, too.
But it's not a simple matter of inheriting an eating-disorder gene. Genetics, family experience, and environmental triggers all play their parts.
Also, today, there is what Bulik calls a "cultural barrage" of enticements to binge.
"Eating disorders are classic examples of gene/environment interactions," Bulik said. "It is more a question of how genetically liable you are. Some people are more sensitive to this cultural barrage.
"Some can go to the food court in the mall, and they won't even smell the food or read the signs because they have low genetic liability," she says. "Whereas for someone with high genetic liability, the food court is a minefield."
One woman Bulik treated for binge eating disorder would go to a particular fast-food restaurant's drive-through window. She'd buy her favorite foods and uncontrollably gobble them while driving, putting herself and others at risk.
As the woman got better, Bulik gave her an assignment: Go to the drive-through window, order the food, but get all the way home before eating.
"But on that day they added these hot cinnamon buns to the menu," Bulik recalled. "She bought six of them, and could not inhibit the urge to eat them all in the car. So all the planning in the world can be undone by a sudden signal that triggers the binge eating."
Binge Eating and Bulimia
Unlike people with bulimia — a closely related eating disorder — people with binge eating disorder don't purge by vomiting or laxative abuse.
But Pope said that while the two conditions are distinct, there is a link.
"My experience after several hundred interviews is that [bulimia and binge eating] are closely related, and it is not uncommon for a person to morph from one to the other," he said.
"Some people have pure bulimia and have always purged and are focused on keeping their weight low," Pope said. "And then there are those in the intermediate category, who occasionally purge. And particularly there are people who are older, whose binge eating came on at a later age, who never thought of purging or just could not get themselves to do it."
Purging, of course, carries its own health risks. But people with binge eating disorder tend to become morbidly obese.
And as binge eating disorder is now known to be much more common that previously thought, it is a big part of the obesity epidemic.
The good news is that eating disorders are treatable.
"We are faced with this incredible obesity epidemic," Bulik said. "We have to ask ourselves what we have in our arsenal to reverse this tide.
"Binge eating is one of those modifiable behavior factors we can focus on as one tool in our arsenal to combat obesity epidemic," she said. "This points to a very substantial minority that we can work with to reduce obesity in a segment of the population."
What Are the Treatments?
"There are basically three forms of treatment," Hudson said.
"One is psychological treatment, especially cognitive and behavioral techniques. This has been effective for binge eating, less so for losing weight," he said.
"The second is medications, especially topiramate [Topamax] and sibutramine [Meridia]," Hudson noted.
"And finally, for individuals with severe obesity, there are surgical procedures, but those are reserved for more severe cases," he said.
Surprise Anorexia Finding
In addition to yielding the first hard data on the extent of binge eating disorder, the survey turned up another surprising finding: Many people with anorexia have a mild version of the disorder.
"This study shows anorexia is not invariably chronic and severe -- although it often is, and I don't want to suggest it cannot be a devastating condition," Hudson said. "But for every anorexia case that comes into the hospital, our data suggests that there are other cases that get better rather quickly."
Hudson said the finding suggests treatment could be improved by finding out which factors are linked to quickly getting over anorexia, and which factors are linked to more severe, chronic anorexia.
SOURCES: Hudson, J. Biological Psychiatry, Feb. 1, 2007; vol 61: pp 348-358. News release, McLean Hospital. News conference with James I. Hudson, MD, ScD, director, psychiatric epidemiology research program, McLean Hospital, Boston; professor of psychiatry, Harvard Medical School, Boston. Harrison Pope Jr., MD, director, biological psychiatry laboratory, McLean Hospital. Cynthia M. Bulik, PhD, professor of eating disorders and nutrition and director, eating disorders program, University of North Carolina at Chapel Hill
By Daniel DeNoon
Reviewed by Louise Chang