Combined exercise and diet are recommended for all persons at increased risk of type 2 diabetes.
The recommendation attaches a relatively high value on the many beneficial effects of the diet used in the studies as well as exercise on other outcomes in addition to diabetes prevention, and the lack of significant adverse effects of these interventions. Diabetes prevention is considered very cost-effective in a societal perspective.
A Cochrane review [Abstract] 1 included 12 studies with a total of 5238 subjects. 11 studies compared diet plus physical activity with standard or no treatment. Study duration ranged from one to six years. Interventions varied between studies but mainly consisted of caloric restriction if the person was overweight, low fat content (especially saturated fat), high carbohydrate content and the increase of fibre intake. Physical activity varied but on average at least 150 minutes each week of brisk walking or other activities such as cycling or jogging were recommended.
Overall, exercise plus diet interventions reduced the risk of diabetes compared with standard recommendations (RR 0.57, 95% CI 0.50 to 0.64; 11 trials; n=4511) and had favourable effects on body weight, waist circumference and blood pressure. No firm conclusion can be drawn about the effectiveness of diet alone or exercise alone in preventing diabetes.
A meta-analysis 2 included 7 RCTs with a total of 4090 subjects. Most of the trials aimed to reduce weight, increase physical activity, and apply a diet relatively low in saturated fat and high in fiber. The overall risk reduction of T2D by the lifestyle interventions was 0.53 (95% CI 0.41 to 0.67).
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