Sert-deficient mice (Sert−/−: KO) were reported to display decreased glucose tolerance, increased deposition of white adipose tissue that increases with aging, and late-onset obesity; these changes were particularly marked in females (Murphy and Lesch, 2008; Üçeyler et al., 2010; Chen et al., 2012; Zha et al., 2017). Here, SLC6A4 is linked to obesity due to melanocortin 4 receptor deficiency.