Finally, a functional polymorphism of the BDNF gene (BDNF Val66Met), which impedes the correct secretion and signaling of BDNF, was correlated with obesity predisposition in children and adolescents (Beckers et al., 2008; Skledar et al., 2012). The gene discussed is BDNF; the disease is obesity due to melanocortin 4 receptor deficiency.