INSIG2 and obesity due to melanocortin 4 receptor deficiency: Since the INSIG2 rs7566605 C-allele has been proposed to exert a larger effect in individuals already predisposed to obesity, we investigated the effect of the variant in the obese subgroup of the combined study sample (n = 3,878), with a mean BMI of 32.8 kg/m2, however, no genotype effect was found (data not shown).