Anorexia is most likely to begin sometime between adolescence and the early 20s, but it can appear in children under the age of 10 or in women as old as 70. Although the disorder receives a great deal of publicity, it's relatively rare. For example, among teenage girls—the group at highest risk—the rate of anorexia is under 1 percent. While the disorder is most common among the middle and upper classes, it occurs in all social classes and ethnic groups.

Certain personality traits increase the risk of developing anorexia. Anorectic girls are often described as "model children" or perfectionists. Many have overcontrolling parents who are themselves fascinated by fitness and appearance. Faced with the impossible task of always being perfect, these girls discover that they can take charge of at least one aspect of their lives by exerting control over their eating and their weight.

Family background may also predispose a woman to anorexia. If you have a mother or sister with anorexia, you are more likely to have the problem than if there were no history of the disorder in your family. However, in a number of cases, there is no familial link.