Laparoscopic banding (where they put a collar on your stomach, the method you are talking about) is highly effective for type II diabetes. That is the method they used in the study I posted earlier which found a 73% remission rate. I believe other studies (which I can’t find right now) have found even higher remission rates, 80%+ for laparoscopic banding.
If bypassing the duodeum and jejunum is necessary to avoid type II diabetes, a new obesity device is being tested which is basically a 10cm sleeve that is inserted inside the intestines to block absorption of food when it passes through these areas. It is safer, cheaper and more reversible than bypass surgery. However it will cause dumping syndrome like bypass surgery does.
Researchers secured a 10-centimeter-long “endoluminal sleeve” at the outlet of the rats’ stomach so it blocked the duodenum and upper jejunum, areas of the small intestine where nutrients are sensed and absorbed. Obese and diabetic rats raised on a high-fat diet given the sleeve consumed 30% less of that diet and lost 20% more weight than their counterparts who did not receive the sleeve. After 16 weeks, the fasting blood glucose levels, insulin levels and oral glucose tolerance of all rats with the sleeve returned to normal levels.