Furthermore, neuroimaging studies have demonstrated altered brain reward responses to food stimuli in patients with monogenic forms of obesity and in individuals with common risk alleles of obesity-associated genes (such as FTO and MC4R) (Heni et al. 2014; Karra et al. 2013; van der Klaauw et al. 2014). Here, FTO is linked to obesity due to melanocortin 4 receptor deficiency.