BDNF and obesity due to melanocortin 4 receptor deficiency: BDNF is also involved in regulating metabolic functions, such as fat oxidation and glucose utilization (Tsuchida et al., 2001; Yamanaka et al., 2007; Matthews et al., 2009), and has been shown to be downregulated in those with obesity and type 2 diabetes (Krabbe et al., 2007; Zhao et al., 2009).