LEP and hepatocellular carcinoma: Subgroup analysis, according to the source of CFC group, showed HCC group had significantly higher leptin levels than the healthy control group (SMD = 4.32, 95% CI (2.41, 6.24), P = 0.000) and the cirrhosis group (SMD = 1.85, 95% CI (0.70, 3.01), P = 0.002), but there was no statistical difference when compared with the chronic hepatitis group (SMD = 0.94, 95% CI (− 0.1, 2.03), P = 0.090) (Fig. 3 and Table 4).