Combined Diet and Physical Activity Promotion Programs to Prevent Type 2 Diabetes Among Persons at Increased Risk: A Systematic Review for the Community Preventive Services Task Force

Abstract

Background: Trials have shown efficacy of rigorous diet and physical activity promotion programs to reduce diabetes incidence and improve glycemic measures in adults at increased risk for type 2 diabetes.

Purpose: To evaluate diet and physical activity promotion programs for persons at increased risk for type 2 diabetes, primarily to reduce diabetes risk and decrease body weight and glycemia.

Data sources: MEDLINE, the Cochrane Central Register of Controlled Trials, CAB Abstracts, Global Health, and Ovid HealthSTAR from 1991 through 27 February 2015, with no language restriction.

Study selection: 8 researchers screened articles for single-group or comparative studies of combined diet and physical activity promotion programs with at least 2 sessions over at least 3 months in participants at increased risk for type 2 diabetes.

Data extraction: 7 researchers extracted data on study design; participant, intervention, and outcome descriptions; and results and assessed study quality.

Data synthesis: 53 studies (30 of diet and physical activity promotion programs vs. usual care, 13 of more intensive vs. less intensive programs, and 13 of single programs) evaluated 66 programs. Compared with usual care, diet and physical activity promotion programs reduced type 2 diabetes incidence (risk ratio [RR], 0.59 [95% CI, 0.52 to 0.66]) (16 studies), decreased body weight (net change, -2.2% [CI, -2.9% to -1.4%]) (24 studies) and fasting blood glucose level (net change, -0.12 mmol/L [-2.2 mg/dL] [CI, -0.20 to -0.05 mmol/L {-3.6 to -0.9 mg/dL}]) (17 studies), and improved other cardiometabolic risk factors. Evidence for clinical events was limited. More intensive programs were more effective.

Limitations: Wide variation in diet and physical activity promotion programs limited identification of features most relevant to effectiveness. Evidence on clinical outcomes and in children was sparse.

Conclusion: Combined diet and physical activity promotion programs are effective at decreasing diabetes incidence and improving cardiometabolic risk factors in persons at increased risk. More intensive programs are more effective.

Primary funding source: Centers for Disease Control and Prevention Community Preventive Services Task Force.

Figure 1

Random-effects model meta-analysis of RR of incident diabetes in at-risk participants in combined diet and physical activity promotion programs vs. usual care. For the meta-analysis of the overall summary risk ratio (RR) of incident diabetes (black diamond), the longest duration of follow-up from each study was used, as indicated by the asterisks and the grey boxes which correspond to the weight of each study in the overall meta-analysis. Subgroup meta-analyses by follow-up time (open diamonds) were conducted for time points with data from at least three studies. CI = confidence interval, Cx = control (usual care), D&PA = combined diet and physical activity promotion program, P_Het = Chi-squared P value of heterogeneity, RD = risk difference, RR = risk ratio. * Included in overall meta-analysis. † To avoid biased meta-analyses due to including correlated analyses, this comparison between the lower intensity intervention and control was excluded from meta-analysis.

Figure 2

Random-effects model meta-analysis of RR of reversion to normoglycemia in at-risk participants in combined diet and physical activity promotion programs vs. usual care. See Figure 1 legend. * Included in overall meta-analysis.

Figure 3

Random-effects model meta-analysis of net percent change in weight (from baseline) in at-risk participants in combined diet and physical activity promotion programs vs. usual care. See Figure 1 legend. Study data closest to 1 year follow-up were included in the overall meta-analysis. * Included in overall meta-analysis. † To avoid biased meta-analyses due to including correlated analyses, this comparison between the lower intensity intervention and control was excluded from meta-analysis.