Individuals with bulimia nervosa regularly engage in bouts of overeating and then compensate for the overeating to avoid gaining weight. Compensation could include various ways of getting rid of the calories such as self-induced vomiting, misuse of laxatives, enemas, diuretics, severe caloric restriction, or excessive exercising. A binge is generally defined as ingesting an amount of food that most others would consider "large" in a similar situation. The individual also notes feeling out of control such that when they start it is difficult for them to stop or that they are unable to prevent the binge from occurring. The binge-purge episodes occur at least twice per week for three months or more. Similar to anorexia nervosa, individuals with bulimia nervosa also have marked concerns about their weight and shape and such concerns influence the way they feel about themselves.

There are two subtypes of bulimia nervosa. First, the purging type describes those who regularly compensate for the binge eating with self-induced vomiting or through the use of laxatives, diuretics, or enemas. Second, the non-purging type is used to describe individuals who compensate through excessive exercising or dietary fasting.