Obesity increases risk of declining physical activity over time in women: a prospective cohort study


  • Author contributions: JT and LT conceived the study. LT organized and supervised the study and analyzed the data. JL, BB, and JT carried out the study. JT had primary writing responsibilities, but all authors were involved in writing the paper and had final approval of the submitted and published versions.

  • Disclosure: The authors have no conflicts of interest to disclose.



Research indicates that risk of obesity increases as physical activity (PA) decreases; however, the reciprocal effect has been rarely studied. The present investigation was conducted to determine the contribution of obesity on objectively measured PA over 20 months.

Design and Methods

A prospective cohort design with 254 middle-aged women was employed. Body fat percentage (BF%) was measured using Bod Pod, and obesity was defined as BF% ≥32%. PA was assessed objectively using 7-day accelerometry at baseline and ∼20 months later at follow-up.


Of the 254 subjects, 124 were obese (49%) at baseline. Mean BF% was 32.1 ± 7.8 and average age was 41.7 ± 3.1 years. Mean weekly PA was 2.79 ± 0.85 million activity counts for all participants. Over the 20-month period, PA decreased significantly more in obese women (−8.1% ± 27.1%) than in nonobese women (0.3% ± 31.7%) after adjusting for confounders (F = 5.3, P = 0.022). Moderate plus vigorous PA levels also decreased more in obese women (−28.1 ± 73.6 min/week) than in nonobese women (−5.9 ± 66.8 min/week), after adjusting for covariates (F = 7.84; P = 0.0055).


It appears that obese women tend to reduce PA over time at a faster rate than nonobese women. Evidently, obesity is a risk factor for decreasing PA over time in middle-aged women.