BDNF and obesity due to melanocortin 4 receptor deficiency: Although mutations, as well as genetic variants, including BDNF Val66Met polymorphism, have been associated with increased body weight and eating disorders in both human and animal models [19,20,21,22,23,31,35,52,53,54,55], the factors and mechanisms involved in the development of obesity in presence of the BDNF Met homozygosity remain to be elucidated.