Progression to type 2 diabetes among people with prediabetes is not inevitable. Modest, sustained weight loss, increased physical activity, and/or metformin therapy in these individuals can prevent or delay the onset of type 2 diabetes.
The National Institutes of Health (NIH)–led Diabetes Prevention Program (DPP) 1 and the Finnish Diabetes Prevention Program 2 aimed for and achieved a mean weight loss of 7 percent and 5 percent, respectively, in lifestyle intervention study participants. Both studies reduced the incidence of diabetes by 58 percent, compared with placebo, over 3 years. In the DPP, these results were similar in all groups, including men and women, all racial and ethnic groups, as well as in women with a history of gestational diabetes. The DPP intensive lifestyle intervention was particularly effective in older participants with 71 percent risk reduction at 3 years. Lifestyle participants followed a healthy low-calorie, low-fat diet and engaged in physical activity of moderate intensity, such as brisk walking, for at least 150 minutes per week. There is some evidence that interventions focused solely on increasing physical activity can contribute to the delay or prevention of type 2 diabetes. 3
In the DPP, metformin reduced type 2 diabetes incidence by 31 percent compared with placebo. Metformin was effective for both men and women, was most effective in younger (25–44 years old) and heavier (body mass index of 35 or higher) people, and was least effective in older people. The Study to Prevent Non-Insulin-Dependent Diabetes Mellitus 4 found that treatment with acarbose, an alpha glucosidase inhibitor that slows the breakdown of complex carbohydrates in the gut, reduced the incidence of type 2 diabetes by 25 percent. Metformin and acarbose have better safety profiles than other diabetes medications that might be considered for prevention, but acarbose is infrequently used in the United States due to significant gastrointestinal side effects.
The follow-up study of the DPP, the Diabetes Prevention Program Outcomes Study (DPPOS), 5 found that at 10 years, lifestyle intervention reduced type 2 diabetes onset by 34 percent and delayed the onset of type 2 diabetes by about 4 years compared with placebo. Because the placebo group received a modified lifestyle intervention at the end of the DPP, the 10-year results may underestimate the effect of lifestyle change. At 10 years, metformin reduced the rate of new diabetes by 18 percent and delayed diabetes onset by 2 years. The DPP lifestyle intervention was cost-effective at 10 years, and there was a very small cost savings with metformin. 6
The DPPOS findings showed continued benefits for study participants in both the lifestyle intervention and the metformin groups at 15 years. Diabetes incidence was reduced by 27 percent among the lifestyle intervention participants and by 18 percent in the metformin group compared with the original placebo group. 7 The cumulative incidences of diabetes at year 15 were 55 percent in the lifestyle group, 56 percent in the metformin group, and 62 percent in the placebo group. There were no overall differences in microvascular outcomes between treatment groups; however, those who did not develop diabetes had a lower prevalence of microvascular complications than those who did develop diabetes. This result supports the importance of diabetes prevention.6