The risk of obesity showed an increasing trend with elevated cystatin C levels before the cystatin C level reached 0.91 mg/L in girls, with the highest risk of obesity (OR = 1.07, 95% CI: 0.88–1.31) at the cystatin C levels of 0.91 mg/L (Figure 2B). Here, CST3 is linked to obesity due to melanocortin 4 receptor deficiency.