IVW results showed that genetic prediction of obesity was associated with eGFRcystatin c (OR = 0.992, 95% CI: 0.990–0.995, P < .05), BUN levels (OR = 1.029, 95% CI: 1.013–1.045, P < .05), and cystatin C levels (OR = 1.042, 95% CI: 1.028–1.056, P < .05) and these causal relationships were also verified in the other 2 methods. Here, CST3 is linked to obesity due to melanocortin 4 receptor deficiency.