Type 2 diabetes affects approximately 8 percent of adults in the United States. Some
risk factors--elevated plasma glucose concentrations in the fasting state and after
an oral glucose load, overweight, and a sedentary lifestyle--are potentially reversible.
We hypothesized that modifying these factors with a lifestyle-intervention program
or the administration of metformin would prevent or delay the development of diabetes.
We randomly assigned 3234 nondiabetic persons with elevated fasting and post-load
plasma glucose concentrations to placebo, metformin (850 mg twice daily), or a lifestyle-modification
program with the goals of at least a 7 percent weight loss and at least 150 minutes
of physical activity per week. The mean age of the participants was 51 years, and
the mean body-mass index (the weight in kilograms divided by the square of the height
in meters) was 34.0; 68 percent were women, and 45 percent were members of minority
The average follow-up was 2.8 years. The incidence of diabetes was 11.0, 7.8, and
4.8 cases per 100 person-years in the placebo, metformin, and lifestyle groups, respectively.
The lifestyle intervention reduced the incidence by 58 percent (95 percent confidence
interval, 48 to 66 percent) and metformin by 31 percent (95 percent confidence interval,
17 to 43 percent), as compared with placebo; the lifestyle intervention was significantly
more effective than metformin. To prevent one case of diabetes during a period of
three years, 6.9 persons would have to participate in the lifestyle-intervention program,
and 13.9 would have to receive metformin.
Lifestyle changes and treatment with metformin both reduced the incidence of diabetes
in persons at high risk. The lifestyle intervention was more effective than metformin.