Average Daily Bout Minutes of Physical Activity Predict Lower BMI Better than Average Daily Minutes

Abstract

PURPOSE: To compare two measures of moderate to vigorous PA as predictors of BMI. Measure 1: Average daily minutes of moderate to vigorous PA Measure 2: Average daily bout minutes of moderate to vigorous PA where a bout is PA lasting for 10 minutes or longer METHODS: We used data from NHANES 2003–2004, a large cross-sectional observational study with a nationally representative sample using a complex sampling design. NHANES participants were asked to wear an accelerometer (Actigraph AM-7164) for 7 consecutive days to record minute-to-minute PA counts. NHANES participants who were at least 18 years of age, not pregnant, had a BMI of at least 20, had data on relevant confounders, and who had valid and reliable accelerometer data for at least 4 days were included in our analysis. We classified each minute as moderate to vigorous activity if the accelerometer activity count was at least 760 activity counts. We calculated average daily minutes of moderate to vigorous activity and average daily bout minutes of moderate to vigorous activity. The primary analysis is a multivariate linear regression accounting for the complex sampling design with average daily bout minutes of PA and average daily minutes of PA as predictors and BMI as the outcome controlling for age, race, income, smoking status, and general health status. RESULTS: Of the 10,122 total NHANES participants, 2757 participants were included in the analysis. Both average daily minutes and average daily bout minutes of moderate to vigorous PA predicted BMI. An increase of 30 minutes in average daily minutes of moderate to vigorous PA leads to a decrease in BMI of 0.23 (p=0.038). An increase of 30 minutes in average daily bout minutes of moderate to vigorous PA leads to a decrease in BMI of 0.65 (p=0.027). Average daily bout minutes of PA are better predictors of BMI than average daily minutes. The r-squared for the final model was 0.10. CONCLUSIONS: This study has shown that both average daily minutes of PA and average daily bout minutes of PA significantly predict lower BMI, however average daily bout minutes are stronger predictors. Supported by NIH Career Development Awards 1K01AG025962-01A2 and K23HL075098