Animal models have shown that the deletion of BDNF in the mouse brain results in obesity, hyperphagia, and impaired locomotor activity (Kernie et al., 2000), and in humans the loss of one copy of the BDNF gene is also associated with hyperphagia, severe obesity, and impaired cognitive function (Gray et al., 2006). This evidence concerns the gene BDNF and obesity due to melanocortin 4 receptor deficiency.