Doctors are reporting a new benefit from weight-loss surgery — preventing diabetes. Far fewer obese people developed that disease if they had stomach-shrinking operations rather than usual care to try to slim down, a large study in Sweden found.

The results, published in Thursday's New England Journal of Medicine, are provoking fresh debate about when adjustable bands and other bariatric procedures should be offered.

It is "provocative and exciting" that surgery can prevent diabetes, but it is "impractical and unjustified" to think of doing it on millions of obese adults, Dr. Danny Jacobs, a Duke University surgeon, wrote in a commentary in the medical journal.