Objectives: To synthesize evidence from randomized controlled trials (RCTs) on the effectiveness of lifestyle interventions to control progression of type 2 diabetes, progression to diabetes from metabolic syndrome, or recurrence of breast cancer and prostate cancer. Lifestyle interventions were defined as any intervention that included exercise, diet, and at least one other component (e.g., counseling, stress management, smoking cessation).
Data Sources: A systematic and comprehensive literature search was conducted to identify RCTs from 1980 to the present.
Review Methods: Study selection, quality assessment, and data extraction were completed by several investigators in duplicate and independently. Random effects models were used for meta-analyses.
Results: From 1,288 citations, we included 20 unique RCTs (plus 80 associated publications): diabetes = 10 studies, metabolic syndrome = 7, breast and prostate cancer = 3. All studies had a “high” or “unclear” risk of bias. Type 2 diabetes: One RCT reported that, at 13 years postintervention, the lifestyle intervention group had fewer nonfatal strokes, reduced incidence of retinopathy, reduced progression of autonomic neuropathy, and reduced incidence of nephropathy. In this trial the lifestyle intervention included pharmacotherapy. A number of studies reported positive effects for lifestyle interventions on changes in body composition, metabolic variables, physical activity, and dietary intake; however, the results were not always statistically significant and were not always sustained following the end of the active intervention. Metabolic syndrome: Four studies reported that lifestyle interventions decreased the risk of developing type 2 diabetes. Most studies also reported positive effects for changes in body composition, metabolic variables, physical activity, and dietary intake. The results were not always statistically significant and were not always sustained following the end of the active intervention. Breast and prostate cancer: One RCT on prostate cancer reported that the lifestyle intervention decreased PSA levels. Two studies reported positive effects for changes in body composition, metabolic variables, physical activity, and dietary intake; however, the results generally were not statistically significant.
Conclusions: Comprehensive lifestyle interventions that include exercise, dietary changes, and at least one other component are effective in decreasing the incidence of type 2 diabetes mellitus in high risk patients and the benefit extends beyond the active intervention phase. In patients who have already been diagnosed with type 2 diabetes, there is some evidence to suggest long-term benefit on microvascular and macrovascular outcomes, although the evidence is from one trial of high risk diabetic patients and included pharmacotherapy. The evidence for lifestyle interventions to prevent cancer recurrence is insufficient to draw conclusions. Comprehensive lifestyle interventions appear to have a positive impact on behavioral outcomes including exercise and dietary intake, as well as a number of metabolic variables, at least in the short-term in all populations addressed in this report.