Lifestyle Interventions for Adults with Impaired Glucose Tolerance: A Systematic Review and Meta-Analysis of the Effects on Glycemic Control

Objective Previous meta-analyses have demonstrated that lifestyle modification can reduce the blood glucose levels in patients with type 2 diabetes, although the effects of changes in the blood glucose level on impaired glucose tolerance (IGT) remain controversial. This review therefore aimed to determine the efficacy of lifestyle interventions in adults with IGT. Methods We searched the Medline, Cochrane Library, EMBASE and Science Citation Index databases and reference lists of the included articles. Two independent reviewers extracted the data and assessed the quality of the included studies; a total of nine randomized controlled trials met the inclusion criteria. In addition, we tested for trial heterogeneity and calculated the pooled effects size using the random effects model. Results The overall interventions were associated with a decline in the 2-hour plasma glucose levels [standardized mean differences (SMD) -0.56; 95% confidence interval (CI), -1.01 to -0.10; I(2), 96.6%]. Moreover, dietary intervention (SMD -0.53; 95% CI -0.77 to -0.28) and physical intervention (SMD -0.42; 95% CI -0.63 to -0.20) were each associated with a decline in the 2-hour plasma glucose levels compared with that observed in the control participants. The overall interventions were associated with a decline in the fasting plasma glucose (FPG) levels (SMD -0.27; 95% CI -0.38 to -0.15; I(2) = 47.1%). In addition, physical intervention (SMD -0.25; 95% CI -0.44 to -0.05) and combined dietary and physical intervention were each associated with a decreased FPG level (SMD -0.28; 95% CI -0.44 to -0.12) compared with that observed in the control participants. Conclusion Lifestyle modification based on physical or dietary interventions or both is associated with improvements in the 2-hour plasma glucose and FPG levels in IGT patients.