A critical role for endogenous BDNF in the regulation of feeding behavior was demonstrated in mice with reduced BDNF levels, such as heterozygous BDNF (Bdnf+/−) mice, which had increased risk of obesity resulting from increased food intake, concomitant with elevated serum leptin and insulin levels (Lyons et al., 1999; Kernie et al., 2000). Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.