Self-selection contributes significantly to the lower adiposity offaster, longer-distanced, male and female walkers
Although cross-sectional studies show active individuals areleaner than their sedentary counterparts, it remains to be determined towhat extent this is due to initially leaner men and women choosing toexercise longer and more intensely (self-selection bias). In this reportwalking volume (weekly distance) and intensity (speed) were compared tocurrent BMI (BMIcurrent) and BMI at the start of walking (BMIstarting) in20,353 women and 5,174 men who had walked regularly for exercise for 7.2and 10.6 years,respectively. The relationships of BMIcurrent andBMIstarting with distance and intensity were nonlinear (convex). Onaverage, BMIstarting explained>70 percent of the association betweenBMIcurrent and intensity, and 40 percent and 17 percent of theassociation between BMIcurrent and distance in women and men,respectively. Although the declines in BMIcurrent with distance andintensity were greater among fatter than leaner individuals, the portionsattributable to BMIstarting remained relatively constant regardless offatness. Thus self-selection bias accounts for most of the decline in BMIwith walking intensity and smaller albeit significant proportions of thedecline with distance. This demonstration of self-selection is germane toother cross-sectional comparisons in epidemiological research, givenself-selection is unlikely to be limited to weight or peculiar tophysical activity.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director, Office of Science; National Institutes ofHealth
- DOE Contract Number:
- DE-AC02-05CH11231; NIHHL-072110, HL-45652 ANDDK066738
- OSTI ID:
- 920064
- Report Number(s):
- LBNL-59333; R&D Project: L0118; BnR: 400412000; TRN: US200822%%710
- Journal Information:
- Iternational Journal of Obesity, Vol. 31, Issue 4; Related Information: Journal Publication Date: 04/2007
- Country of Publication:
- United States
- Language:
- English
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