Listed in the Diagnostic and Statistical Manual of Mental Disorders, anorexia nervosa is characterized by:
Refusal (not inability) to maintain body weight at or above 85 percent of what is expected based on age and height.
Intense fear of gaining weight or becoming fat, even though underweight.
Disturbance in the way one's body weight or shape is experienced, undue influence of body weight or shape on self-evaluation, or denying the seriousness of one's own low body weight.
For girls and women, cessation of menstrual periods for at least three consecutive cycles.
Two subtypes of the disorder are:
Restricting — in which the person loses weight primarily through dieting, fasting or excessive exercise.
Bingeing and purging — in which the person regularly engages in eating binges, followed by vomiting.