Anorexia is an eating disorder identified, in part, by a refusal to eat, an intense desire to be thin, repeated dieting attempts, and excessive weight loss. The disease affects from 0.5 percent to 1 percent of the female adolescent population, and its average age of onset is between 14 and 18 years. People with anorexia believe they are fat even when they are dangerously thin. Although people with the disorder are often characterized as perfectionists and overachievers who appear to be in control, they actually suffer from low self-esteem and overly criticize themselves. Some of the things that they may do in order to maintain an abnormally low weight include dieting, fasting, and over-exercising, as well as misusing laxatives, diuretics, or enemas. Treatment often includes therapy and nutritional counseling. More severe cases may require hospitalization.