LEP and hepatocellular carcinoma: Stratification by albumin levels of HCC patients showed HCC group had significantly higher leptin levels than CFC group in “< 3.5 g/dl” (SMD = 3.47, 95% CI (1.28, 5.66), P = 0.002), but not in the “≥ 3.5 g/dl” (SMD = 0.12, 95% CI (− 0.02, 0.26), P = 0.091).