Binge eating is defined as eating more food than most people would eat in a similar timeframe and associating that consumption with a feeling of a loss of control. The behavior to prevent weight gain is called "compensatory behavior." The compensatory behavior usually takes one of the following forms: purging by self-induced vomiting, or excessive use of enemas or laxatives; or non-purging by excessive exercise, fasting for long periods before binge eating again, or in the case of a person with diabetes, omitting insulin intake.

Bulimia nervosa is listed as a mental health disorder in the Diagnostic and Statistical Manual of Mental Disorders Volume IV (DSM-IV). This manual is the 4th edition of a diagnostic reference book by the American Psychiatric Association that lists mental disorders and describes the characteristics or criteria used to diagnose each disorder. Individuals with a diagnosis of bulimia nervosa often have a co-existing disorder such as obsessive-compulsive disorder (OCD), major depressive disorder, or substance abuse. People who fit many, but not all, of the criteria may be given a diagnosis of "eating disorder, not otherwise specified" or ED-NOS, which is also listed in the manual.

The clinical terms used for the disorder and the criteria listed in the manual have changed several times over the past 25 years. At times the disorder was called just "bulimia," but now is clinically referred to as bulimia nervosa, which we use throughout this resource guide.