FTO and obesity due to melanocortin 4 receptor deficiency: The genotypes of CC or TC (as compared to the TT genotype) at the FTO variant upregulate expression of FTO in skeletal muscle (https://gtexportal.org/home/snp/rs1421085), which is a major component of SLM; it is known that an upregulation of FTO can result in increased food intake leading to obesity (Church et al., 2010).