TCF7L2 and obesity due to melanocortin 4 receptor deficiency: Studies have shown that several obesity-related genes (such as appetite regulation genes: FTO, MC4R, LEP, LEPR; energy metabolism genes: ADRB3, PPARG, UCP1; insulin resistance genes: TCF7L2, IRS1; biological clock and neuroregulatory genes: CLOCK, BDNF) have mutations or polymorphisms that affect appetite regulation, fat storage, energy expenditure, and metabolic function, increasing the individual’s susceptibility to obesity (8–13).