FTO and obesity due to melanocortin 4 receptor deficiency: The FTO gene modulates the activity of the midbrain reward circuitry by regulating the activity of the receptors D2 and D3 (Hess et al., 2013; Sevgi et al., 2015; Heni et al., 2016), providing a potential mechanism for the increased risk for obesity associated to the FTO risk-variants.