In the United States, about 24 million adults have diabetes, and up to 95 percent of them have type 2 diabetes. This type of diabetes is strongly associated with obesity, inactivity, family history of diabetes, history of gestational diabetes, impaired glucose metabolism and racial or ethnic background. The prevalence of diabetes has more than doubled in the last 30 years, due in large part to the upsurge in obesity.

An additional 57 million overweight adults have glucose levels that are higher than normal but not yet in the diabetic range, a condition that substantially raises the risk of a heart attack or stroke and of developing type 2 diabetes.

"In 10 years, participants in the lifestyle changes group delayed type 2 diabetes by about four years compared with placebo, and those in the metformin group delayed it by two years," said study chair David M. Nathan, M.D., of Massachusetts General Hospital. "The benefits of intensive lifestyle changes were especially pronounced in the elderly. People age 60 and older lowered their rate of developing type 2 diabetes in the next 10 years by about half."

White said the participants in the DPPOS will be followed for another five years to get information on complications associated with diabetes and prediabetes over time, including eye, kidney and heart disease.

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