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The Diabetes Prevention Program (DPP) was a major clinical trial, or research study, aimed at discovering whether either diet and exercise or the oral diabetes drug Metformin (Glucophage) could prevent or delay the onset of type 2 diabetes in people with Impaired Glucose Tolerance (IGT).
The answer is yes, they both can. In fact, the DPP Study found that over 3 years, beneficial changes in diet and physical activity greatly reduced the chances that a person with IGT would develop diabetes. Metformin also reduced risk, although less dramatically. The DPP resolved these questions so quickly that, on the advice of an external monitoring board, the program was halted a year early. The researchers published their findings in the February 7, 2002, issue of the New England Journal of Medicine.
DPP Study Design and Goals
In the DPP, participants from 27 clinical centers around the country were randomly split into different treatment groups. The first group, called the lifestyle intervention group, received intensive training in diet, exercise, and behavior modification. By eating less fat and fewer calories and exercising for a total of 150 minutes a week, participants aimed to lose 7% of their body weight and maintain that loss.
The second group took 850 mg of Metformin twice a day. The third group received placebo pills instead of Metformin. The Metformin and placebo groups also received information on diet and exercise, but no intensive counseling efforts. A fourth group was treated with the drug Troglitazone (Rezulin). This part of the study was discontinued after researchers discovered that Troglitazone can cause serious liver damage.
All 3,234 study participants were overweight and had IGT, which are well recognized risk factors for the development of type 2 diabetes. In addition, 45 percent of the participants were from minority groups – African American, Hispanic American/Latino, Asian American or Pacific Islander, or American Indian – that are at increased risk of developing diabetes.
The DPP’s striking results tell us that diet, exercise, and behavior modification, delays and may prevent the development of type 2 diabetes. The DPP also suggests that Metformin is effective in delaying (or preventing) the onset of diabetes.
Participants in the lifestyle intervention group–those receiving intensive counseling on effective diet, exercise, and behavior modification–reduced their risk of developing diabetes by 58%. This finding was true across all participating ethnic groups and for both men and women. Lifestyle changes worked particularly well for participants aged 60 and older, reducing their risk by 71%. About 5% of the lifestyle intervention group developed diabetes each year during the study period, compared with 11% in those who did not get the intervention. Researchers think that weight loss–achieved through better eating habits and exercise–reduces the risk of diabetes by improving the body’s ability to use insulin and process glucose.
Participants taking Metformin reduced their risk of developing diabetes by 31%. Metformin was effective for both men and women, but it was less effective in people aged 45 and older. Metformin was most effective in people 25 to 44 years old and in those with a body mass index of 35 or higher (at least 60 pounds overweight). About 7.8% of the Metformin group developed diabetes each year during the study, compared with 11% of the group receiving the placebo.
NIH Publication No. 06–5099