Efficacy of interventions that include diet, aerobic and resistance training components for type 2 diabetes prevention: a systematic review with meta-analysis

Current recommendations for the prevention of type 2 diabetes advise modification of diet and exercise behaviors including both aerobic and resistance training. However, the efficacy of multi-component interventions involving a combination of these three components has not been established. The aims of this review were to systematically review and meta-analyze the evidence on multi-component (diet + aerobic exercise + resistance training) lifestyle interventions for type 2 diabetes prevention. Eight electronic databases (Medline, Embase, SportDiscus, Web of Science, CINAHL, Informit health collection, Cochrane library and Scopus) were searched up to June 2013. Eligible studies 1) recruited prediabetic adults or individuals at risk of type 2 diabetes; 2) conducted diet and exercise [including both physical activity/aerobic and resistance training] programs; and 3) reported weight and plasma glucose outcomes. In total, 23 articles from eight studies were eligible including five randomized controlled trials, one quasi-experimental, one two-group comparison and one single-group pre-post study. Four studies had a low risk of bias (score ≥ 6/10). Median intervention length was 12 months (range 4–48 months) with a follow-up of 18 months (range 6.5 - 48 months). The diet and exercise interventions varied slightly in terms of their specific prescriptions. Meta-analysis favored interventions over controls for weight loss (-3.79 kg [-6.13, -1.46; 95% CI], Z = 3.19, P = 0.001) and fasting plasma glucose (-0.13 mmol.L(-1) [-0.24, -0.02; 95% CI], Z = 2.42, P = 0.02). Diabetes incidence was only reported in two studies, with reductions of 58% and 56% versus control groups. In summary, multi-component lifestyle type 2 diabetes prevention interventions that include diet and both aerobic and resistance exercise training are modestly effective in inducing weight loss and improving impaired fasting glucose, glucose tolerance, dietary and exercise outcomes in at risk and prediabetic adult populations. These results support the current exercise guidelines for the inclusion of resistance training in type 2 diabetes prevention, however there remains a need for more rigorous studies, with long-term follow-up evaluating program efficacy, muscular fitness outcomes, diabetes incidence and risk reduction.