Eating disorders are complex. From the outset it should be understood that they are real, treatable medical illnesses and potentially fatal. However, unlike many other illnesses the cause of an eating disorder is often a complicated mix of psychological, physiological and social factors. Eating disorders often appear in the early teens (for both girls and guys) and start out slow. The sufferer will often begin by eating smaller or larger amounts than normal which then spirals out of control. Disorders are usually divided into four categories: Anorexia Nervosa, Bulimia Nervosa, Binge Eating and eating disorders not otherwise specified (EDNOS).