Long-Term Parallel Changes of Physical Activity and Body Mass Index in Different Predisposing Risk Trajectories of Obesity

Abstract

Background: The long-term parallel changes of physical activity and body mass index (BMI) in the adult population are still unclear. The present study assessed the association between physical activity and BMI over time, considering obesity risk trajectory groups and sex strata. Methods: Total sample of 6897 adults was followed for an average of 12 years. The reliable and validated Iranian version of the Modifiable Activity Questionnaire measured physical activity. After determining the risk clusters in each reexamination using a 2-step cluster analysis, the latent growth curve modeling was used to identify distinct subgroups of individuals following a similar change of risk cluster over time. Latent growth curve modeling estimated the parameters of cross-sectional, prospective, and parallel associations. Results: Three trajectories were identified, including stable low risk, unstable risk, and stable high risk. The results showed significant increases in BMI (kg/m2/year) for the stable low-risk trajectory group 0.478 (95% confidence interval [CI] 0.444 to 0.513), unstable risk 0.360 (95% CI, 0.324 to 0.396), and those in the stable high-risk trajectory group 0.255 (95% CI, 0.221 to 0.289). In cross-sectional −0.483 kg/m2 (95% CI, −0.836 to −0.129) and parallel −0.93 kg/m2 (95% CI, −1.862 to 0.00) estimations, significant statistical associations were observed in the stable high-risk trajectory group. Conclusions: The current results showed that changes in physical activity could slightly affect BMI only in stable high-risk adults.