Similar to the core roles of IL-33, ILC2s, IL-4, and IL-10 in the maintenance of homeostasis, MCP-1 and leptin play initial and critical roles in obesity-induced chronic inflammation through the recruitment of monocytes, which then polarize into M1s, and also via the aggregation of other inflammatory immune cells. Here, CCL2 is linked to obesity due to melanocortin 4 receptor deficiency.