FTO is related to human obesity and mental development and was the first m6A mRNA demethylase identified to convert mRNA m6A to adenosine in mRNA (Dina et al., 2007; Loos and Yeo, 2014; Mauer et al., 2017; Wei et al., 2018). Here, FTO is linked to obesity due to melanocortin 4 receptor deficiency.