UCP1 and obesity due to melanocortin 4 receptor deficiency: External factors, such as cold exposure and β3-adrenergic receptor (β3-AR) agonists (Cypess et al. 2015) or peroxisome proliferator-activated receptor gamma (PPARγ) agonists (Petrovic et al. 2010), can induce WAT browning, leading to UCP1-dependent thermogenesis and increased resistance to obesity.