According to current evidence, macrophages progressively infiltrate the adipose tissue during obesity, initiate the pro-inflammatory response by producing tumor necrosis factor-α (TNF-α) and interleukin (IL)-6, and block adipocyte insulin action, a contributing factor in the development of IR and type 2 diabetes mellitus (19, 20). This evidence concerns the gene TNF and obesity due to melanocortin 4 receptor deficiency.