FTO and obesity due to melanocortin 4 receptor deficiency: Briefly, the weight of Fto-KO mice was lower than that of WT mice when the mice were fed HFD (WT 45.4 g (1.07) vs. KO 32.3 g (1.64), p < 0.001), indicating a resistance to diet-induced obesity, while the energy intake was unchanged between the two groups.