On one hand, the increased activity of cytochrome P450 (CYPs) (CYP2C9, CYP1A2, CYP2E1, and CYP2D6) in individuals with obesity could augment generation of toxic metabolites (Brill et al., 2012). The gene discussed is CYP2D6; the disease is obesity due to melanocortin 4 receptor deficiency.