Lifestyle changes are better for delaying diabetes in patients with IGT

Clinical question Are lifestyle changes (diet and exercise) more effective than metformin in delaying the onset of diabetes in patients with impaired glucose tolerance (IGT)?

Bottom line Patients with impaired glucose tolerance who make intensive lifestyle changes are less likely to develop diabetes than patients who take metformin or a placebo, even if they are not able to maintain weight loss. (Level of evidence = 1b–)

Synopsis In the original Diabetes Prevention Program (DPP) report on 3,244 patients with IGT (N Engl J Med. 2002;346[6]:393-403), patients who engaged in lifestyle changes (losing and maintaining a 7% weight loss plus 150 minutes per week of moderate intensity exercise) were less likely to develop diabetes than patients who took metformin (850 mg twice a day). Both lifestyle and metformin were more effective than placebo (number needed to treat [NNT] = 7 for lifestyle; NNT = 14 for metformin). This paper provides 10-year follow-up data for 2,766 (85%) of the original participants (4.3 years of follow-up in the original study plus 5.7 years in this study). After the initial phase of the DPP, patients in each group were offered diet and exercise education sessions every 3 months. Additionally, patients in the lifestyle group were given four additional sessions and patients in the metformin group continued to take the drug, but in unmasked fashion. The researchers evaluated the patients every 6 months. The overall loss to follow-up was comparable for each group. The main outcome—the development of diabetes—was defined as a fasting plasma glucose level above 7.0 mmol/L (126 mg/dL) or a 2-hour glucose level above 11.1 mmol/L (200 mg/ dL) after a 75-g glucose load. Patients in the intensive lifestyle group initially lost weight but regained much of their original weight over time. In the initial DPP study, the overall rate of developing diabetes in the lifestyle group was 4.8 cases per 100 person-years compared with 7.8 in the metformin group and 11.0 in the placebo group. During the follow-up study, the subsequent incidences were comparable for each intervention (5.3, 6.4, and 7.8 per 100 person-years, respectively), meaning that the gains seen in the initial study were maintained.

Diabetes Prevention Program Research Group, Knowler WC, Fowler SE, et al. 10-year follow-up of diabetes incidence and weight loss in the Diabetes Prevention Program Outcomes Study. Lancet. 2009;374(9702):1677-1686.