Eating disorders are marked by extremes. People with an eating disorder may severely reduce the amount of food they eat, or eat an unusually large amount of food, or be extremely concerned about their weight or shape. They may start out simply eating smaller or larger portions than usual, but at some point the urge to eat more or less spirals out of control.

There are three main types of eating disorders: anorexia nervosa, bulimia nervosa, and binge-eating disorder. People with anorexia nervosa see themselves as overweight even though they are dangerously thin from starving themselves. People with bulimia nervosa eat unusually large amounts of food (binge eat) and then compensate by purging (vomiting, taking laxatives or diuretics), fasting or excessive exercise. People with binge-eating disorder binge but do not purge, and they often become overweight or obese. Eating disorders may occur along with depression, substance abuse, or anxiety disorders, and can cause heart and kidney problems, even death. The disorders show up most frequently during teenage years, but there are indications they may develop earlier or later in life.Why some people are at risk for eating disorders isn’t clear. But surveys show that depression is often a factor. In a 2008 study by researchers at the University of Pittsburgh Medical Center, for example, 24% of bipolar patients met the criteria for eating disorders. An estimated 44% had trouble controlling their eating. As many as half of all patients diagnosed with binge eating disorder have a history of depression, according to the National Institute of Diabetes and Digestive andKidney Diseases. Binge eating afflicts 3% of adults in the U.S., making it the most common eating disorder.