A meta-analysis of 13 prospective cohort studies published in 2009 showed an inverse monotonic association between adiponectin levels and the risk of type 2 diabetes [relative risk (95% CI): 0.72 (0.67–0.78) per 1–log μg/mL increment in adiponectin levels], although most of those studies were conducted in Western populations with a high prevalence of obesity [14]. This evidence concerns the gene ADIPOQ and obesity due to melanocortin 4 receptor deficiency.