The major risk factors for obesity are environmental and genetic, and several candidate genes are involved in obesity in mice and humans, including glucose transporter type 4 (Glut4), leptin, adiponectin, tumor necrosis factor (TNF-α), interleukin 6 (IL-6), interleukin 1β (IL-1β), monocyte chemotactic protein 1 (MCP-1), glucose-6-phosphate (G6P), and phosphoenolpyruvate carboxykinase (PEPCK) [1, 7–11]. The gene discussed is CCL2; the disease is obesity due to melanocortin 4 receptor deficiency.