The prevalence of anorexia nervosa has increased in recent years, and a large proportion of adults as well as adolescents with this disorder have low bone density and, therefore, an increased risk of fractures. Anorexia nervosa often begins during adolescence, when peak bone mass is accumulated, resulting in significant deficits in bone mass accrual. Therefore, it is important to determine bone mineral density in adolescent and adult women who have this disorder, and to improve or at least stabilize bone metabolism in those with low bone mass. To do this, it is necessary to understand the mechanisms underlying low bone density in anorexia nervosa. This article discusses current concepts related to bone loss associated with anorexia nervosa, including how to prevent it.