Winer and colleagues reported the importance of VAT resident CD4+ T lymphocytes as modulators of insulin sensitivity in mice under diet-induced obesity; glucose homeostasis was compromised when pathogenic IFN-γ-secreting Th1 cells accumulated in adipose tissue and overwhelmed the static numbers of Th2 and Treg cells. This evidence concerns the gene INS and obesity due to melanocortin 4 receptor deficiency.