We next evaluated plasma levels of IL-4, which was found to be reduced in patients with obesity and IR compared with lean patients (BMI ≥ 30 kg/m2 [11.4 ± 2.0 pg/mL] versus BMI < 25 kg/m2 [23.3 ± 5.3 pg/mL], P = 0.05) (Figure 3E). This evidence concerns the gene IL4 and obesity due to melanocortin 4 receptor deficiency.