Weight-loss surgery works much better than standard medical therapy as a treatment for Type 2 diabetes in obese people, the first study to compare the two approaches has found.

The study, of 60 patients, showed that 73 percent of those who had surgery had complete remissions of diabetes, meaning all signs of the disease went away. By contrast, the remission rate was only 13 percent in those given conventional treatment, which included intensive counseling on diet and exercise for weight loss, and, when needed, diabetes medicines like insulin, metformin and other drugs.

In the study, the surgery worked better because patients who had it lost much more weight than the medically treated group did  20.7 percent versus 1.7 percent of their body weight, on average. Type 2 diabetes is usually brought on by obesity, and patients can often lessen the severity of the disease, or even get rid of it entirely, by losing about 10 percent of their body weight. Though many people can lose that much weight, few can keep it off without surgery. (Type 1 diabetes, a much less common form of the disease, involves the immune system and is not linked to obesity.)

But the new results probably do not apply to all patients with Type 2 diabetes, because the people in the study had fairly mild cases with a recent onset; all had received the diagnosis within the previous two years. In people who have more severe and longstanding diabetes, the disease may no longer be reversible, no matter how much weight is lost.