We have previously shown that circulating levels of several cytokines are modified in overweight and obesity and other studies have shown interleukin 6 (IL-6) to be a marker of fetal adiposity and a stimulator for amino acid transport [31], [39], [40], but these and similar factors have not been considered in the current study. Here, IL6 is linked to obesity due to melanocortin 4 receptor deficiency.