INS and obesity due to melanocortin 4 receptor deficiency: Increased expression of the gene encoding FGF21 in females possibly contributed to their lower susceptibility to the development of obesity, insulin resistance, and hypercholesterolemia, since FGF21 increases energy expenditure through the activation of thermogenesis in BAT [47], activates fatty acid oxidation in the liver [48], increases insulin sensitivity [31], and helps to reduce blood cholesterol levels [49].