Bariatric surgery resulted in 39 with 3,855 participants in significant reductions in fasting blood glucose (FBG) (WMD: −0.82 mg/dL; 95%CI: −0.92 to −0.72), postprandial glucose (PPG) (WMD: −4.15 mg/dL; 95%CI: −5.38 to −2.92), Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) levels (WMD: -2.81; 95% CI: −3.06 to −2.56), C-peptide (WMD: -0.38; 95%CI: −0.73 to −0.03) and fasting insulin (WMD: -0.62; 95% CI: −0.88 to −0.36). This evidence concerns the gene INS and Insulin resistance.