ObjectiveTo investigate the effect of the remnant stomach after gastric bypass (GB) surgery on the weight loss and glucose metabolism in rats with obese and type 2 diabetes mellitus (T2DM).MethodsHigh fat feeding for one month combined with intraperitoneal injection of low-dose streptozotocin was used to induce obese rats with T2DM. Twenty-four rats with obese and type T2DM successfully established were randomly divided into resectional gastric bypass (R-GB) group, GB surgery (GB group), and sham operation (SO) group, eight rats in each group. The weight loss and anti-diabetic effect of the R-GB and GB were compared. Body weight, food intake, and fasting blood glucose (FBG) were measured at week 1 before operation and week 1–8 after the operation. Oral glucose tolerance test (OGTT) and insulin tolerance test (ITT) were performed using tail venous blood at week 1 before operation and on week 8 after operation (at 0, 30, 60, 90, and 120 min). The levels of serum glucagon like peptide-1 (GLP-1), gastrin, insulin, and glucagon at week 1 before operation and at week 8 after operation were detected, meanwhile the homeostasis model assessment insulin resistance (HOMA-IR) index was calculated.Results① The body weight and food intake of the rats in the R-GB group and GB group were lower than those in the SO group after operation (P<0.05) and which were lower than before operation (P<0.05), but the differences were not significant between the R-GB group and GB group after operation (P>0.05). ② The levels of FBG in the R-GB group only at week 1–4 after operation were lower than those before operation (P<0.05), while which in the GB group at week 1–8 after operation were lower than those before operation and were lower than in the SO group (P<0.05), but which in the R-GB group only at week 2–4 after operation were lower than in the SO group and which were higher than that in the GB group from 3 to 8 weeks after operation (P<0.05). ③ The area under receiver operating characteristic curves (AUCs) of blood glucoses of OGTT and ITT and HOMA-IR index at week 8 after operation were lower than those before operation (P<0.05) in the GB group and which were lower than those the other two groups (P<0.05). ④ The AUC of gastrin level at week 8 after operation was lower than that before operation in the R-GB group and which lower than that in the other two groups (P<0.05). The AUC values of insulin and glucagon levels at week 8 after operation were lower than those before operation in the GB group and which lower than those in the other two groups (P<0.05). The AUC of GLP-1 level at week 8 after operation was higher than that before operation in the GB group and which higher than that in the other two groups (P<0.05).ConclusionsGB could remarkably improve glucose metabolism and weight loss in obese rat with T2DM. Gastric remnant gastrectomy following GB has a remarkable anti-diabetic effect, but it doesn’t effect on weight loss.