The prevalence of anorexia nervosa is 0.5-1%. The prevalence among males in this age range is about one-tenth that of females. The mortality rate in anorexia nervosa is 6%. I. Pathophysiology
A. This disorder is characterized by: 1) a body weight that is below normal (ie, <85% of expected body weight); 2) intense fears of weight gain despite being underweight; 3) body image disturbance resulting in the misperception of one's weight or shape, undue self-evaluation based upon weight, or denial of the seriousness of the current low weight; and 4) in post-menarchal females, the absence of at least three consecutive menstrual cycles. The diagnosis of anorexia nervosa requires all four criteria.
B. Restricting type anorexia nervosa is characterized by restrictive eating patterns. Binge-eating/purging type anorexia nervosa is characterized by binge-eating episodes followed by purging behavior.
C. A binge consists of rapid intake of 2500 calories or 2.5 times the normal amount of food. Binges are characterized by a lack of control over food intake during a period of less than 2 hours.
D. Purging behaviors entail acute and active efforts to eradicate ingested calories and may include self-induced vomiting and/or the use of laxatives, diuretics, or enemas.
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