INS and obesity due to melanocortin 4 receptor deficiency: In fact, while in mice the activation of BAT and the promotion of WAT browning ameliorate insulin sensitivity, liver steatosis and glucose tolerance in obesogenic conditions (Wang et al., 2015; Kimura et al., 2021), the impact of WAT browning on obesity or insulin resistance in humans is less relevant (Barquissau et al., 2018; Comas et al., 2019).