TH and obesity due to melanocortin 4 receptor deficiency: In particular, lower mRNA expression and higher DNA methylation of the tyrosine hydroxylase (TH) gene—the rate limiting enzyme in the synthesis of dopamine—was measured in the brains of mice and rats exposed to high fat and high sugar diets (Li et al., 2009; Lee et al., 2010; Vucetic et al., 2012; Robinson et al., 2015), and lower dopamine reuptake and evoked release were observed in rats fed a high fat diet for 6 weeks in the absence of obesity (Cone et al., 2013).