Objective measurements of sedentary behavior are less associated with recall bias (which may differ by obesity status), and they reduce measurement error and improve the ability to determine the strength and direction of association. In those studies, sedentary behavior has been defined either by the amount of time spent watching television ( 9, 10) or by the absence of regular participation in sports and strenuous physical activity ( 13). Previous studies examining the prospective and longitudinal associations between sedentary behavior and BMI have relied on self-reported data ( 9, 10, 13).
Three longitudinal studies suggested that a high baseline BMI predicts sedentary behavior or physical inactivity, whereas those studies provided no compelling evidence for a long-term influence of physical inactivity on gains in BMI or the development of obesity ( 11– 13). However, because persons who are overweight or obese may be less likely to stay active, it is not fully clear whether obesity is a cause or a consequence of sedentary behavior. Others have suggested that sedentary behavior predicts gain in body weight or BMI ( 9, 10), an association that appeared to be independent of exercise levels and other confounding factors ( 9). More recently, a review of the literature on the prospective associations between baseline physical activity and gain in body weight or BMI suggested that low levels of baseline physical activity were only weakly related to such gain ( 8). In prospective population-based cohort studies, subjects who report higher levels of leisure-time physical activity or regular participation in exercise are less likely to gain in weight or body mass index (BMI), although the results have been somewhat inconsistent ( 6, 7). Although obesity is multifactorial, including genetic, biological, cultural, and socioeconomic components, it is likely that an imbalance between energy intake and energy expenditure (EE) is the main underlying cause of the current epidemic ( 4, 5). Obesity, which is increasing in prevalence in most parts of the world, is considered as one of the greatest health challenges of the 21st century ( 1– 3). In contrast, BW (β = 0.33 95% CI: 0.15, 0.50), BMI (1.10 0.58, 1.63), FM (0.59 0.11, 0.40), and WC (0.44 0.23, 0.66) predicted sedentary time at follow-up after adjustment for sex, baseline age, baseline sedentary time, baseline physical activity energy expenditure, and follow-up time.Ĭonclusion:BMI, FM, and WC may predict sedentary time, but our results do not suggest that sedentary time predicts future obesity. Sedentary time did not predict any of the obesity indicators at follow-up. Results:At baseline, sedentary time was significantly correlated with FM (partial r = 0.10, P = 0.043) and WC (partial r = 0.11, P = 0.027) after adjustment for sex and age. All measurements were collected at baseline and at 5.6-y follow-up. Fat mass (FM) was assessed with bioimpedance. Body weight (BW), body mass index (BMI), and waist circumference (WC) were assessed by standard clinical procedures. Sedentary time (% of daytime hours) was measured by individually calibrated monitoring of the heart rate.
Objective:We aimed to assess the longitudinal associations between objectively measured time spent being sedentary (sedentary time) and obesity indicators.ĭesign:The study was a prospective, population-based cohort study in 393 middle-aged healthy whites ( n = 176 M, 217 F). Background:Whether obesity is a cause or a consequence of a sedentary lifestyle has not yet been fully elucidated, which leaves uncertainty about the direction of causality.
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