In the present study, we observed that a risk allele of rs5945326 near DUSP9 tended to increase HOMA-IR (β = 0.066, p = 0.0769; Table 4), and subsequent BMI-stratified analysis showed that the effects of the rs5945326-A allele could be observed only in the non-obese group (BMI<25, β = 0.099, p = 0.0198; Table 4, Table S9) but not in obese group (BMI≥25, β = -0.035, p = 0.6423); the effect of rs5945326-A on reducing insulin sensitivity might be masked by obesity-induced insulin resistance in the obese group. This evidence concerns the gene DUSP9 and obesity due to melanocortin 4 receptor deficiency.