Obesity can induce changes in metabolism and gene expression in adipocytes, thereby enhancing lipolysis and releasing proinflammatory free fatty acids (FFAs) and cytokines (such as monocyte chemotactic protein-1 (MCP-1) and tumor necrosis factor-alpha (TNF-α)), which are able to recruit and activate macrophages to produce high levels of proinflammatory mediators (such as TNF-α, interleukin-1 beta (IL-1β), and resistin). Here, CCL2 is linked to obesity due to melanocortin 4 receptor deficiency.