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

Objective 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. Results 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). Conclusions 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.