By increasing leptin levels, obesity alters adipose tissue macrophages’ (ATMs) metabolism through Janus kinase 3 (JAK3) and STAT3, and PI3K-Akt-mTOR pathways, increasing glycolytic enzymes’ activity and glucose uptake as well as inducing mitochondrial dysfunctions (247). This evidence concerns the gene STAT3 and obesity due to melanocortin 4 receptor deficiency.