medwireNews: The authors of the single diabetes-related Cochrane review published in December find moderate-quality evidence for the ability of diet plus exercise to ward off type 2 diabetes in people with impaired glucose tolerance (IGT).
However, there was little evidence for the effects of diet or exercise alone versus standard treatment or each other, with just one to two low-quality trials making these comparisons.
For the review, which is an update of a 2008 one, Bianca Hemmingsen (Herlev University Hospital, Denmark) and colleagues identified 12 randomized controlled trials, involving 5238 people, which lasted for at least 2 years.
Eleven of the trials compared diet plus exercise with standard treatment, and nine of these based their high-risk assessment on IGT, meaning there was little evidence for the effects of diet and exercise in high-risk people identified by other definitions, such as impaired fasting glucose or elevated glycated hemoglobin.
Across these eleven trials, which were of moderate quality, 315 of 2122 participants in the diet and exercise groups developed type 2 diabetes, compared with 614 of 2389 in the comparator groups, giving a significant 43% risk reduction overall. There was a 50% risk reduction in an analysis restricted to trials with a low risk of selection bias. The three trials with extended follow-up reported that the protective effects of diet plus exercise persisted for up to 23 years.
But the review authors stress: “Data on patient-important outcomes such as mortality, macrovascular and microvascular diabetic complications and health-related quality of life are sparse.”
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