IL6 and obesity due to melanocortin 4 receptor deficiency: Finally, we used the presence of overweight and obesity as a covariate, because it was observed that an adipose tissue, particularly visceral fat, releases some pro-inflammatory cytokines, such as CRP, interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) (Kwon and Pessin 2013), and in that way overweight and obesity might confound the relationship.