CST3 and obesity due to melanocortin 4 receptor deficiency: In model 2, taking the cystatin C first quartile level as the reference, the risks of obesity were elevated by four-, three-, and two-fold in the second quartile (OR = 3.85, 95% CI: 1.46–8.13, P = 0.006), third quartile (OR = 2.90, 95% CI: 1.06–7.97, P = 0.038), and fourth quartile (OR = 2.45, 95% CI: 0.90–6.65, P = 0.078) cystatin C levels, respectively.