A possible reason for this finding is the drastically low fat mass, which brings about a metabolic adaptation in form of a down-regulation of REE, possibly mediated by leptin as shown in many previous studies on REE in female patients with anorexia nervosa [32]; another possible reason could be the metabolic adaptation at the physical activity, considering that professional ballet dancers have biomechanical changes and functional performance related to intense dance training [33]. This evidence concerns the gene LEP and anorexia nervosa.