Meanwhile, activated macrophages secrete monocyte chemoattractant protein 1 (MCP‐1), which promotes a large number of monocytes to be recruited into the obesity‐associated adipose tissue in humans and mice by binding with chemokine (C‐C motif) receptor 2 on the surface of monocytes, further differentiated into macrophages and polarised into pro‐inflammatory M1 macrophages [146, 147]. Here, CCL2 is linked to obesity due to melanocortin 4 receptor deficiency.