CCL2 and obesity due to melanocortin 4 receptor deficiency: As CCL2 levels are elevated in obesity and is associated with inflammation and insulin resistance, and as exercise lowers CCL2 levels, the aim of this study was to test the hypothesis that CCL2 levels are higher in obese children when compared to lean controls, and that CCL2 levels are higher in children with low fitness levels when compared to fit children reflecting a more robust inflammatory response.