STAT1 and obesity due to melanocortin 4 receptor deficiency: Given our finding that STAT1 adipocyte gene expression was higher in human obesity (Fig. 4f) and increases after overfeeding (Fig. 3e), and that IFNγ-mediated increases in STAT1 can impair Treg differentiation15, we next examined the effects of IFNγ and its signaling through the JAK/STAT1 pathway on metabolic genes.