FTO and obesity due to melanocortin 4 receptor deficiency: The first genetic loci were detected via variants in intron 1 of the FTO (fat mass and obesity associated gene; e.g., [1]–[4]) and variants approx. 200 kb downstream of MC4R (melanocortin 4 receptor gene; [5]–[8]) reported by the GIANT (Genetic Investigation of ANthropometric Traits) consortium.