After adjustment for measured and reported potential confounders, adults who reported more than six hours of sedentary time per day had 7.1% higher odds of having a higher BMI and 12.5% higher odds of abdominal obesity than the reference category. The corresponding 95% confidence intervals were 1.016–1.130 for BMI and 1.074–1.178 for abdominal obesity. In the other direction, qualified moderate-to-vigorous physical activity was associated with 10.7% lower odds of higher BMI and 11.3% lower odds of abdominal obesity, with confidence intervals of 0.860–0.927 and 0.860–0.914, respectively. These are observational associations, not evidence that changing either behavior would directly cause the estimated change in obesity odds.

The clearest evidence of a sex difference appeared in the relationship between physical activity and abdominal obesity. The formal interaction between sex and qualified moderate-to-vigorous physical activity was significant for BMI at p = 0.002 and for abdominal obesity at p less than 0.001. Sex-stratified estimates showed that the inverse association with abdominal obesity was stronger in men: qualified activity was associated with an odds ratio of 0.874, with a 95% confidence interval of 0.845–0.904, compared with 0.924, with a 95% confidence interval of 0.863–0.991, in women. The researchers therefore described the pattern as potentially sex-specific, while the study design cannot establish whether men and women respond differently to an equivalent increase in activity.

Sedentary time showed a different pattern. Its interaction with sex was significant for abdominal obesity at p = 0.003, suggesting that the association between sitting time and central adiposity varied between men and women. No significant sex interaction was detected for sedentary time and BMI, at p = 0.161. Although the sex-stratified estimates differed numerically, the investigators cautioned that the observed difference for BMI should be treated as exploratory rather than as evidence of a distinct sex effect. The distinction matters because an apparent difference in separate subgroup estimates does not, by itself, demonstrate that the underlying associations differ between groups.

The findings are limited by the retrospective design, the use of questionnaire-based behavioral measurements and the fact that participants came from a health management center rather than a population-representative national sample. Participants also had repeated measurements, and the analysis used generalized estimating equations to account for observations within individuals, but unmeasured factors could still influence both behavior and body composition. The results offer a detailed picture of adjusted associations: more sitting was linked to worse BMI and abdominal-obesity outcomes, while qualifying levels of moderate-to-vigorous activity were linked to lower odds. The sex-interaction results add nuance, especially for activity and abdominal obesity, but further research is needed before the findings can guide sex-tailored obesity-prevention strategies or support causal conclusions.

Subject of Research: Sex-specific associations of physical activity and sedentary time with obesity in Chinese adults

Article Title: Sex-specific associations of physical activity and sedentary time with obesity: a longitudinal study in China

Article References: Cao, H., Li, Y., Dong, X., Wang, X., Luo, J., Huang, M., Duan, Y., He, X., Yang, P., Wang, Y., Xie, J., Wang, S., & Ng, P. H. F. (2026). Sex-specific associations of physical activity and sedentary time with obesity: a longitudinal study in China. BMC Public Health. https://doi.org/10.1186/s12889-026-29697-9

Image Credits: AI Generated

DOI: 10.1186/s12889-026-29697-9

Keywords: physical activity, sedentary time, obesity, abdominal obesity, BMI, sex differences, Chinese adults, longitudinal cohort, Sex-specific, associations, physical, activity