Anorexia nervosa is an eating disorder in which the afflicted individual avoids eating or eats extremely little out of an irrational fear of becoming or being fat. This fear/perception of being fat does not diminish as the individual loses weight (often to a dangerous extent -- some individuals may lose up to 25% of their original weight). This condition is most common among young women (ages 12 to 21) but is also found in men (particularly athletes, dancers, etc.) and in older women.