BDNF and obesity due to melanocortin 4 receptor deficiency: Regarding the relationship between BDNF polymorphisms and obesity, the BDNF G196A (Val66Met) polymorphism (rs6265) was chosen as one of the two tags in the present study because this common BDNF polymorphism affects intracellular packaging of the precursor of BDNF (proBDNF) [11].