Prospective associations between sedentary lifestyle and BMI in midlife.
OBJECTIVE
A strong positive cross-sectional relationship between BMI and a sedentary lifestyle has been consistently observed in numerous studies. However, it has been questioned whether high BMI is a determinant or a consequence of a sedentary lifestyle.


METHODS
Using data from four follow-ups of the University of North Carolina Alumni Heart Study, we examined the prospective associations between BMI and sedentary lifestyle in a cohort of 4595 middle-aged men and women who had responded to questionnaires at the ages of 41 (standard deviation 2.3), 44 (2.3), 46 (2.0), and 54 (2.0).


RESULTS
BMI was consistently related to increased risk of becoming sedentary in both men and women. The odds ratios of becoming sedentary as predicted by BMI were 1.04 (95% confidence limits, 1.00, 1.07) per 1 kg/m(2) from ages 41 to 44, 1.10 (1.07, 1.14) from ages 44 to 46, and 1.12 (1.08, 1.17) from ages 46 to 54. Controlling for concurrent changes in BMI marginally attenuated the effects. Sedentary lifestyle did not predict changes in BMI, except when concurrent changes in physical activity were taken into account (p < 0.001). The findings were not confounded by preceding changes in BMI or physical activity, age, smoking habits, or sex.


CONCLUSIONS
Our findings suggest that a high BMI is a determinant of a sedentary lifestyle but did not provide unambiguous evidence for an effect of sedentary lifestyle on weight gain.
Mortensen
Laust H
LH
National Institute of Public Health, Øster Farimagsgade 5, 1399 Copenhagen K, Denmark. lmo@niph.dk.
Siegler
Ilene C
IC
Barefoot
John C
JC
Grønbaek
Morten
M
Sørensen
Thorkild I A
TI
D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007899:Leisure Activities; D008019:Life Style; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011446:Prospective Studies; D012044:Regression Analysis