Anorexia nervosa (AN) concerns 1% of adolescent girls and happens at a time of intense bone growth. Adolescents who develop AN before or during puberty have growth retardation and may not achieve their genetic height potential. Osteopenia, as evidenced by dual-energy X-ray absorptiometry, is also frequent. The degree of osteopenia depends on the age of onset and the duration of AN. The role of estrogen deficiency is no more considered paramount with regards to other factors like the fall of growth factor IGF1. The prevention of osteopenia in AN relies mostly on early nutritional intervention. Hormone replacement therapy or calcium/vit D supplements are not sufficient to improve bone density in undernourished patients. New therapeutic strategies combining anabolic and antiresorptive agents are being developed.