the onset of menarche is dependent on fat stores; and once initiated, as little as a 10 to 15 percent decrease in weight can cause menstruation to stop.13,44-45 According to Frisch and McArthur, an 18-year-old girl needs about 35 pounds of fat to maintain normal menstruation.46 This is the reason anorexia nervosa is associated with irregular or absent menstruation. It also explains why female marathon runners and ballerinas frequently have irregular menses.47
