On a molecular level, obesity is characterized by high levels of IL-6 in white adipose tissue that, in turn, chronically activate intracellular JAK-STAT3 signaling and increase the expression of suppressor of cytokine signaling-3 (SOCS-3), which negatively regulates IL-6 signaling, hinders insulin action, and eventually results in obesity and insulin resistance. Here, STAT3 is linked to obesity due to melanocortin 4 receptor deficiency.