In accordance with these studies, case reports of patients with anorexia nervosa provide initial evidence in humans that an alleviation of hypoleptinemia via application of human recombinant leptin reduces the drive for activity and PA [21, 22].This finding together with the well-known urge to move and increased physical activity in patients with anorexia nervosa [47, 48] had led to our focus on lean children. The gene discussed is LEP; the disease is anorexia nervosa.