A large federal study of whether diet and weight loss can prevent heart attacks and strokes in overweight and obese people with Type 2 diabetes has ended two years ahead of schedule because the intensive program did not help.
“I was surprised,” said Rena Wing, the study’s chairwoman and a professor of psychiatry and human behavior at Brown University’s medical school.
Like many, she had assumed diet and exercise would help, in part because short-term studies had found that those strategies lowered blood sugar levels, blood pressure and cholesterol levels.
But, Dr. Wing added, “You do a study because you don’t know the answer.”
Still, medical experts said there were many benefits to diet and exercise even if they did not reduce cardiovascular disease in people with diabetes.
About 25 million Americans have Type 2 diabetes. Many are overweight or obese. On average, the disease increases heart disease risk by 2 to 2 ½ times, said Dr. Ronald Kahn, chief academic officer at the Joslin Diabetes Center in Boston.
It seemed logical that diet and exercise would help reduce that risk. An earlier federal study found that an intense diet and exercise program helped prevent overweight or obese people with elevated blood sugar levels from crossing the line into diabetes. The hope was that a similar program could also protect people from heart disease.
The study randomly assigned 5,145 overweight or obese people with Type 2 diabetes to either a rigorous diet and exercise regimen or to sessions in which they got general health information. The diet involved 1,200 to 1,500 calories a day for those weighing less than 250 pounds and 1,500 to 1,800 calories a day for those weighing more. The exercise program was at least 175 minutes a week of moderate exercise.
But 11 years after the study began, researchers concluded it was futile to continue — the two groups had nearly identical rates of heart attacks, strokes and cardiovascular deaths.
The investigators are analyzing their data and will be publishing them in research papers.
But the outcome is clear, said Dr. David Nathan, a principal investigator and director of the Diabetes Center at Massachusetts General Hospital. “We have to have an adult conversation about this,” he said. “This was a negative result.”