"I see it all the time, every day. 'I can only have three pieces of broccoli and a spoonful of cottage cheese. How about you?" she says. "Who can be the most disciplined in their eating?"

But once students leave the pressure-cooker of college, their eating problems often decrease, Heatherton says.

The five percent of Harvard women who have clinical eating disorders is higher than the general population average of two percent, though Harvard's numbers are typical of most competitive high schools and colleges.

"We have data from people 10 years out of college and most people get a lot better once they get out of college," Heatherton says.

Bulimia Nervosa

Bulimia, a disorder characterized by frequent binge eating and purging, is widely believed to be the most common clinical eating disorder at Harvard.

Nationally, bulimia occurs in five percent of college-aged women, and more than 90 percent of bulimic patients are female, according to the New York-based American Anorexia/Bulimia Association.

Sufferers may use vomiting, laxatives, diuretics, enemas, fasting or excessive exercise to purge their food. Those who have the disease purge twice a week on average for three months or more.

Concerned with their weight and body image, they also lack control over their eating patterns, according to the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders.

For Lena, bulimia began in high school, when she started dieting even though she was "very, very thin."

Purging seemed like the perfect solution, she says.

"I wanted to lose weight. I wanted the golden key," she says. "I wanted to be able to eat whatever I wanted and not worry."

After failing several times to make herself throw up, Lena took a drug to induce vomiting. Eventually, Lena says, she could do it at will.

"At the worst I was throwing up maybe 30 times in one day. Basically one sitting would consist of maybe 15 times," she recalls.

"Sometimes I would sit down and know I would purge afterwards," she says. "Other times I would sit down just to do it, almost in a trance. Certainly there was no physiological hunger."