TNF and obesity due to melanocortin 4 receptor deficiency: Obesity can lead to a state of low grade systemic inflammation, which is associated with increased circulating pro-inflammatory cytokines [e.g. tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6)] and adipokines (e.g., leptin) and an increase in pro-inflammatory macrophages within adipose tissue (7–9).