1. Continued use of metformin beyond the randomized controlled trial was found to be predictive of long-term weight loss among participants who had lost at least 5 percent of their body weight during the first year of the trial.
2. The authors observed that older age and greater amount of weight loss in the first year of the study were independent predictors of long-term weight loss.
Evidence Rating Level: 2 (Good)
Study Rundown: Type 2 diabetes has many associated morbidity and mortality risks and is a significant burden of disease in North America. Weight loss is an important factor in preventing and/or delaying the development of Type 2 diabetes. The authors of this study conducted post hoc analysis of data from the Diabetes Prevention Program (DPP), a randomized controlled trial to identify predictors of long-term weight loss (LTWL). They observed that among patients who had lost at least 5 percent of their body weight during the first year of the trial, patients who continued to take metformin sustained the greatest amount of weight loss in long-term follow up. Furthermore, greater weight loss within the first year of the study was predictive of overall greater long-term weight loss. One of the strengths of this study was that the DPP had a significant long-term follow-up to assess weight loss and diabetes prevention among patients. A limitation of this study was that even though the initial DPP study was a RCT, the post hoc analysis was a secondary analysis and assessed nonrandomized subsets of the groups after the first year.
In-Depth [post hoc analysis]: The authors conducted a post hoc analysis of the Diabetes Prevention Program (DPP) randomized controlled trial, in order to identify predictors of LTWL. The randomized controlled trial was carried out from July 1996 to July 2001 and compared weight loss of participants using metformin, intensive lifestyle intervention (ILS), or placebo. The second phase of the study was a long-term follow-up (DPP Outcomes Study) where weight changes were observed among 88.5% of participants at 10 and 15 years. To analyze the data, the authors utilized fixed-effects models and generalized estimating equation models to estimate the percentage of participants with LTWL that had lost at least 5% of weight within the first year of the study. The authors observed that the greatest mean weight loss compared to baseline maintained between years 6 and 15 was within the metformin group (6.2% 95% CI, 5.2% to 7.2%). These weight loss results were followed by the ILS group (3.7%, CI 3.1% to 4.4%) and then the placebo group (2.8% CI 1.2% to 4.4%). Additionally, the authors found independent LTWL predictors to be greater weight loss in the first year, older age and continued use of metformin in the metformin group.
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