LEP and breast cancer: In the subgroup analysis of ethnicity, the mean leptin levels were significantly higher in patients with BC in Asian population (SMD = 1.29, 95% CI = 0.91–1.68, P <.0001) or Caucasian population (SMD = 0.23, 95% CI = 0.09–0.37, P = .001) (Fig. 2).