Objective Physical Activity Accumulation in Bouts and Nonbouts and Relation to Markers of Obesity in US Adults

INTRODUCTION: Little is known about the relation between duration of physical activity and obesity. The objective of this study was to compare the effects of physical activity in bouts (≥10 minutes) to the effects of physical activity in nonbouts (<10 minutes) on markers of obesity. METHODS: We used data from the 2003-2004 National Health and Nutrition Examination Survey on body mass index, waist circumference, and objectively determined physical activity levels for 3,250 adults aged 18 years or older. After controlling for relevant confounding variables, we performed multiple linear regression analyses to predict body mass index and waist circumference for bout and nonbout minutes of moderate- to vigorous-intensity physical activity (MVPA) and for bout and nonbout accelerometer counts of physical activity. RESULTS: MVPA bout minutes and MVPA nonbout minutes are independently associated with body mass index and waist circumference, after controlling for confounding variables. The strength of the association between lower body mass index and MVPA bout minutes (β = −0.04, P <.001) was nearly 4 times greater than for MVPA nonbout minutes (β = −0.01, P = .06). For smaller waist circumference the association was nearly 3 times greater for MVPA bout minutes (β = −0.09, P <.001) than for MVPA nonbout minutes (β = −0.03, P = .01). Bout minutes of physical activity were at a higher intensity of activity compared with nonbout minutes of physical activity. CONCLUSION: Accumulating MVPA in nonbouts may be a beneficial starting point for individuals to increase physical activity levels and decrease body mass index and waist circumference. However, bouts of physical activity lasting ≥10 minutes may be a more time-efficient strategy to decrease body mass index and waist circumference.