Anorexia Nervosa and bulimia nervosa are characterized by severe disturbances of eating behavior. The salient feature of anorexia nervosa (AN) is a refusal to maintain a minimally normal body weight. Bulimia nervosa (BN) is characterized by recurrent episodes of binge eating followed by abnormal compensatory behaviors, such as self-induced vomiting. AN and BN are distinct clinical syndromes but share certain features in common. Both disorders occur primarily among previously healthy young women who become overly concerned with body shape and weight. Many patients with BN have past histories of anorexia nervosa, and many patients with anorexia nervosa engage in binge eating and purging behavior. In the current diagnostic system, the critical distinction between AN and BN depends on body weight: patients with AN are, by definition, significantly underweight, whereas patients with BN have body weights in the normal range or above.

Binge eating disorder (BED) is a more recently described syndrome characterized by repeated episodes of binge eating, similar to those of BN, in the absence of inappropriate compensatory behavior. Patients with BED are typically middle-aged men or women with significant obesity. They have an increased frequency of anxiety and depression compared to similarly obese patients without BED. It is not known whether patients with BED are at increased risk for medical complications or what treatment strategies are indicated.