Moreover, alterations in BDNF levels as a function of the Val66met polymorphism have also been implicated in appetite regulation and food intake (Lebrun et al., 2006), eating disorders (Chen et al., 2004), obesity (Zhao et al., 2009), and metabolic disorders (Krabbe et al., 2007), providing evidence that BDNF might play an important role in the pathophysiology of these conditions. Here, BDNF is linked to obesity due to melanocortin 4 receptor deficiency.