LEP and metabolic syndrome: In men with a BMI of 20 to < 25, participants with leptin > 97.5th group had significantly higher levels of HOMA-IR, LDL-C, UA, a higher proportion of central obesity (WC > 90 cm), metabolic syndrome, and lower levels of HDL-C than participants with leptin of 2.5th to ≤ 97.5th group (Additional file 1: Table S2).