As in obesity, aging is frequently associated with increased fat tissue and circulating pro-inflammatory cytokines secreted by dysfunctional fat cells, including tumor necrosis factors-α (TNF-α) and interleukin (IL-6)86, which in turn alter T lymphocyte subsets and attract mast cells and cause monocyte recruitment and macrophage activation89. The gene discussed is TNF; the disease is obesity due to melanocortin 4 receptor deficiency.