In patients with knee OA and BMI ≥ 30 kg/m2 serum levels of leptin (39.546 ± 12.918 ng/mL) were significantly higher as compared with the control group, which was comprised of individuals with different BMIs, including cases with obesity but without OA (15.832 ± 16.531 ng/mL, p < 0.05) (Figure 1A). This evidence concerns the gene LEP and obesity due to melanocortin 4 receptor deficiency.