The results are "quite remarkable" and could revolutionize care, said one independent expert, Dr. Robert Siegel, a cardiologist at Cedars-Sinai Medical Center in Los Angeles.
"No one dreamed, at least I didn't," that obesity surgery could have such broad effects long before it caused patients to lose weight, he said. Some patients were able to stop using insulin a few days after surgery.
At three years, "more than 90 percent of the surgical patients required no insulin," and nearly half had needed it at the start of the study, said its leader, Dr. Philip Schauer of the Cleveland Clinic. In contrast, insulin use rose in the medication group, from 52 percent at the start to 55 percent at three years.
The results were reported Monday at an American College of Cardiology conference in Washington. They also were published online by the New England Journal of Medicine.
Doctors are reluctant to call surgery a possible cure because they can't guarantee diabetes won't come back.
But some patients, like Heather Britton, have passed the five-year mark when some experts consider cure or prolonged remission a possibility. Before the study, she was taking drugs for diabetes, high blood pressure and high cholesterol; she takes none now.
"It's a miracle," said Britton, a 55-yeear-old computer programmer from suburban Cleveland.
"It saved my life. I have no doubt that I would have had serious complications from my diabetes" because the disease killed her mother and grandmothers at a young age, she said.
About 26 million Americans have diabetes, and two-thirds of them are overweight or obese. Diabetes is a leading cause of heart disease, strokes, kidney failure, eye trouble and other problems.
It's treated with various drugs and insulin, and doctors urge weight loss and exercise, but few people can drop enough pounds to make a difference. Bariatric surgery currently is mostly a last resort for very obese people who have failed less drastic ways to lose weight.
It costs $15,000 to $25,000 and Medicare covers it for very obese people with diabetes. Gastric bypass is the most common type: Through "keyhole" surgery, doctors reduce the stomach to a small pouch and reconnect it to the small intestine. Another type is sleeve gastrectomy, in which the size of the stomach is reduced less drastically.
Schauer's study tested these two operations versus medication alone in 150 mildly obese people with severe diabetes. Their A1c levels — a key blood-sugar measure — were over 9 on average at the start. A healthy A1c is 6 or below and the study aimed for that, even though the American Diabetes Association sets an easier target of 7.
After three years, researchers had follow-up on 91 percent of the original 150 patients. The medication group's A1c averaged 8.4; the surgery groups were at 6.7 and 7, with gastric bypass being a little better.