anorexia: An eating disorder in which a person has an irrational fear of getting fat and therefore diets excessively to stay thin. Such a person is referred to variously as an anoretic, anorectic, or anorexic.

behavioral therapy: Therapy that tries to change a person's behavior by giving rewards or privileges for appropriate behavior. For example, an anoretic who gains weight will be rewarded with something she likes.

binge: To eat or drink excessively.

binge eating: An eating disorder in which a person eats large quantities of food. A person who is binge eating feels out of control and cannot stop the behavior, even when he or she wants to quit.

Body Mass Index (BMI): A measurement designed to show whether a person is underweight, normal weight, or overweight. It is based on a relationship between height and weight. Although designed for the metric system (kilograms and meters), there...