Most Asian patients undergoing metabolic surgery for the treatment of T2DM have BMI as low as 30-35 kg/m2. If SG is performed for the treatment of T2DM in these patients, weight may decrease after the surgery; however, T2DM may recur after 6 months to 1 year. Therefore, it is difficult to find clinical studies on SG for metabolic surgery in Asians, and gastric bypass may be more appropriate as metabolic surgery. However, gastroscopy for the remnant stomach after gastric bypass is practically impossible. Therefore, gastric bypass may be a fatal drawback for East Asian patients with a high incidence of gastric cancer. In recent years, modified duodenal switch (SG with duodenojejunal bypass [DJB], which is defined as the procedure that makes jejunal bypass shorter than the traditional duodenal switch) is often performed as metabolic surgery, and studies on this surgical technique are being actively conducted in Japan.~SG with DJB has both effects of stomach restriction and foregut bypass. However, SG with DJB is more disadvantageous compared to SG alone in nutrient absorption after surgery. This is a natural result of bypassing the duodenum and proximal jejunum. Therefore, SG with DJB should not be performed when it is unnecessary, and it should be performed in patients who are expected to show significant improvement in T2DM. However, there is no existing guideline on which patients can receive SG with DJB or SG alone, and there are also no clinical studies on these aspects.
In this study, the effects of SG with DJB and SG alone for the treatment of type 2 diabetes mellitus (T2DM) will be compared in patients other than the two groups at both extremes who are expected to show excellent effects of metabolic surgery with SG alone (mild T2DM) and who need SG with DJB (severe T2DM).~This study is to target patients with poor blood sugar control despite current medical treatment, although the beta-cell function of the pancreas is preserved. Therefore, this study is aimed at patients who have been using insulin for less than 10 years with T2DM, or taking diabetic medications with HbA1c ≥ 7.0% for less than 10 years with T2DM.~The investigators hypothesize that the treatment effects of SG with DJB for T2DM will be superior to that of SG in this group