The TSMR analysis by the IVW method showed a significant causal effect, wherein each SD of genetically higher BMI was associated with an increased T2DM risk [OR: 2.741; 95% confidence interval (CI): 2.421–3.104], higher fasting glucose [1.073; 1.048–1.099], higher fasting insulin [1.202; 1.173–1.231], higher HOMA-IR [1.221; 1.187–1.255], and higher HbA1c [1.054; 1.04–1.068]. Here, INS is linked to type 2 diabetes mellitus.