In the early stage of obesity, chemotactic monocyte chemoattractant protein-1 (MCP-1)/C-C chemokine receptor 2 (CCR2) are secreted by hypertrophic adipocyte, in which the cytokines promote the accumulation of macrophage in obese adipose tissue. The gene discussed is CCL2; the disease is obesity due to melanocortin 4 receptor deficiency.