Out-of-control binge eating is the biggest eating disorder in the United States, more common than anorexia and bulimia combined and contributing to a rise in obesity, researchers said on Thursday.

Binge eating afflicts 3.5 percent of U.S. women and 2 percent of men at some point in their lives, according to a study by psychiatric researchers at Harvard University Medical School and its affiliate, McLean Psychiatric Hospital.

“I suspect that the connection that we have drawn in this study is just the tip of the iceberg of the problem of out-of-control eating and its relationship to obesity,” Dr. James Hudson, the study’s lead author, told Reuters.

He said binge eating - where people cannot stop from eating well beyond the point of being full at least twice a week - is a chronic and persistent condition in the United States that is under-reported and under-diagnosed.

“The most striking finding of the study is the emergence of binge eating as a major public-health problem,” Hudson said.

The researchers surveyed more than 9,000 people from 2001 to 2003 in the first national survey of eating disorders.

It said about 0.9 percent of women and 0.3 percent of men reported suffering at some point from anorexia nervosa - a disorder characterized by refusing to eat and an obsessive desire to be thin. It said 1.5 percent of women and 0.5 percent of men reported the condition of bulimia, in which binge eating is followed by attempts to compensate by methods such as self-induced vomiting or excessive use of laxatives or exercise.

It also found a “surprisingly high” proportion of men with anorexia and bulimia - at one-fourth of the reported cases for each of those disorders.

‘ASHAMED’

“We believe that the estimates for binge-eating disorder are really under-estimates. That people are often very ashamed of this behavior, and for everyone who is willing to talk about it in a face-to-face interview there are others who don’t bring it up or don’t elaborate,” Hudson said.

Health risks include obesity, diabetes, heart disease, high blood pressure and stroke, the researchers said.

There was no scientific explanation for binge eating, although genes and easy access to food could play a role, said Hudson. A typical binge eater might follow a full dinner with a quart of ice cream and bag of chips without being able to stop.

Anorexia typically lasts 1.7 years, compared to 8.3 years for bulimia and 8.1 years for binge eating, the study said.

“Contrary to what people may believe, anorexia is not necessarily a chronic illness. In many cases, it runs its course and people get better without seeking treatment. So our survey suggests that for every one severe case of anorexia, there may be many other milder cases,” the researchers said.