OBJECTIVE: To observe the efficacy and therapeutic effect of gastric diversion surgery (GBP) on overweight, obese and non-obese patients with type 2 diabetes mellitus (T2DM), for which we followed up the pattern of glucose metabolism changes after GBP in overweight obese and normal weight patients in both groups. METHODS: From January 2006 to June 2007, 103 patients with T2DM were enrolled in the general surgery department of the Armed Forces General Hospital, and the patients were divided into two groups according to body mass index (BMI): overweight obese group: BMI ≥ 25, and normal weight group: BMI < 25. The postoperative follow-up periods were six months, one year, two years, and three years, and glycated hemoglobin and BMI, OGTT, insulin release test, and C-peptide release test were observed, respectively. The glycated hemoglobin and BMI, OGTT, insulin release test and C-peptide release test were observed respectively. Results: ①In the 3-year follow-up period, the overall efficiency of T2DM was 87%, among which the efficiency of overweight obese group was 91% and the efficiency of normal weight group was 77%; ②Compared with the preoperative BMI, the postoperative BMI of overweight obese group decreased significantly, 62 overweight obese patients had BMI <24kg/m2, and the efficiency was 95%, but there was no significant change in the BMI of normal weight group; ③Compared with the normal weight group Compared with the preoperative insulin secretion value of patients, the insulin secretion value ΔI30/ΔG30 was significantly higher 3 years after surgery, and the difference was significant; ④ Compared with the preoperative HOMA-IR, the overweight obese group had significantly improved HOMA-IR 3 years after surgery, and the difference was significant. Conclusion: GBP has significant therapeutic effect on both overweight obese and normal weight T2DM, but the significant rate of T2DM in normal weight group is lower than that in overweight obese group, showing that its hypoglycemic effect is independent of the weight loss effect, while the overweight obese group mainly depends on the improvement of insulin resistance after surgery.