However, increasing numbers of studies have indicated that circulating RBP4 levels are associated with cardiometabolic diseases such as obesity [8], insulin resistance [9], hyperlipidaemia [10], hypertension [11], chronic liver diseases [12–14], atherosclerosis [15] and cardiovascular disease [16–20]. Here, RBP4 is linked to obesity due to melanocortin 4 receptor deficiency.