Abstract: Objective To evaluate the therapeutic effects of laparoscopic Roux-en-Y gastric bypass (LRYGB) and laparoscopic duodenal-jejunal bypass with sleeve gastrectomy (SADJB-SG) in patients with type 2 diabetes mellitus and a low body mass index (BMI) of 25-27.5. Methods Thirty-one type 2 diabetic patients with a BMI of 25-27.5 underwent bariatric surgeries in the General Hospital of Guangzhou Military Command between August, 2013 and August, 2015. The patients receiving LRYGB (17 cases) and SADJB-SG (14 cases) were compared for physical indexes, glucose metabolism and of pancreatic islet function at 1 year after the surgeries. Results No mortality occurred in the patients after the operations. At 1 year after the operation, the patients in LRYGB group showed significant improvements in body weight, BMI, glycated hemoglobin (HbA1c), fasting plasma glucose (FPG), oral glucose tolerance test 2 h (OGTT2h), C-peptide, fasting insulin (FINS), and postprandial 2 hour insulin (2 hPINS) (P<0.05); in SADJB-SG group, significant improvements were observed in the body weigh, BMI, HbA1c, FPG, OGTT2h, and FINS after the operation (P<0.05). The postoperative improvements in body weigh, BMI, HbA1c, FPG, OGTT2h, C-peptide, and 2hPINS were comparable between SADJB-SG group and LRYGB group (P>0.05), but the incidence of postoperative anastomotic ulcer was lower in SADJB-SG group. Conclusion SADJB-SG and LRYGB produce similar therapeutic effects in type 2 diabetic patients with a low BMI, but SADJB-SG is associated with a low incidence of postoperative complications and is therefore more suitable in such patients.