title: Objectively measured moderate- and vigorous-intensity physical activity but not sedentary time predicts insulin resistance in high-risk individuals.
abstract: 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.
  
  
  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.
authors.affiliation: Medical Research Council, Epidemiology Unit, Cambridge, UK. ulf.ekelund@mrc-epid.cam.ac.uk
authors.forename: Ulf
authors.initials: U
authors.lastname: Ekelund
authors.forename: Soren
authors.initials: S
authors.lastname: Brage
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Griffin
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Wareham
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology; D000375:Aging; D015992:Body Mass Index; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology* / Q000235:genetics; D019317:Evidence-Based Medicine; D015444:Exercise / Q000502:physiology*; D005190:Family; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D008019:Life Style; D008297:Male; D009043:Motor Activity; D011237:Predictive Value of Tests; D012146:Rest / Q000502:physiology*; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects; D013690:Television; D055105:Waist Circumference
chemical_list: D007328:Insulin