Objectively Measured Moderate- and Vigorous-Intensity Physical Activity but Not Sedentary Time Predicts Insulin Resistance in High-Risk Individuals

OBJECTIVE Low levels of physical activity appear to be associated with insulin resistance. However, the detailed associations of these complex relationships remain elusive. We examined the prospective associations between self-reported TV viewing time, objectively measured time spent sedentary, at light-intensity activity, and at moderate- and vigorous-intensity physical activity (MVPA) with insulin resistance. RESEARCH DESIGN AND METHODS In 192 individuals (81 men and 111 women) with a family history of type 2 diabetes, we measured physical activity and anthropometric and metabolic variables at baseline and after 1 year of follow-up in the ProActive UK trial. Physical activity was measured objectively by accelerometry. Insulin resistance was expressed as fasting insulin and the homeostasis model assessment score (HOMA-IR). RESULTS Baseline MVPA was a significant predictor of fasting insulin at follow-up (beta = -0.004 [95% CI -0.007 to -0.0001], P = 0.022), and the association approached significance for HOMA-IR (beta = -0.003 [-0.007 to 0.000002], P = 0.052), independent of time spent sedentary, at light-intensity activity, sex, age, smoking status, waist circumference, and self-reported TV viewing. Time spent sedentary and at light-intensity activity were not significantly associated with insulin resistance. The change in MVPA between baseline and follow-up was inversely related to fasting insulin (beta = -0.003 [-0.007 to -0.0003], P = 0.032) and the HOMA-IR score (beta = -0.004 [-0.008 to -0.001], P = 0.015) at follow-up, after adjustment for baseline phenotype in addition to the same confounders as above. CONCLUSIONS These results highlight the importance of promoting moderate-intensity activity such as brisk walking for improving insulin sensitivity and possibly other metabolic risk factors to prevent type 2 diabetes.