BN is characterized by three main symptoms:
- Recurrent episodes of binge eating, in which the person eats a very large amount of food in a discrete period of time (e.g., a two-hour period). During these eating binges the person experiences a sense of loss of control, or a sense that he/she is unable to stop eating or control what or how much he/she is eating.
- Recurrent inappropriate compensatory behaviors, in which the person attempts to prevent weight gain. Common compensatory behaviors include self-induced vomiting, misusing laxatives or other medications, fasting, or exercising excessively.
- Overemphasis on body weight and shape, including a very strong influence of weight and shape on the individual's self-esteem.
For an individual to be diagnosed with BN, eating binges and accompanying purging behaviors must occur, on average, at least once per week for three months or longer. If these behaviors are associated with significantly low body weight and occur within the context of anorexia nervosa, anorexia nervosa (binge-eating/purging type) would be diagnosed instead of BN.
Several factors can be useful to distinguish a binge from normal overeating. The definition of "a very large amount of food" is subjective, but is usually defined as an amount that is significantly greater than most individuals would eat in a similar situation. Often the individual will feel uncomfortably or painfully full after a binge. Individuals with BN often describe a sense of dissociation or complete inability to control their food consumption once a binge has started, and they may eat foods they might otherwise avoid. These binges often lead the individual to feel ashamed; consequently, many individuals with BN will binge and purge in secret. These individuals may not be forthcoming about their binging or purging behaviors due to guilt, shame, or fear of stigma.