Physical activity (PA) is suggested to increase the peak bone mass and to minimize age-related bone loss, and thereby to reduce the risk of osteoporosis. However, the relation between PA and bone health considering the obesity status is unclear so far. The present study examines the association between PA levels and calcaneal broadband ultrasound attenuation (BUA), particularly under consideration of obesity. Data from a population-based sample of 6776 German women from the EPIC-Potsdam cohort were analyzed. Calibrated PA data were used. Statistical analyses were stratified by menopausal and obesity status. Multiple linear regression was used to model the relationship between PA and BUA levels after adjustment for age, body mass index (BMI), smoking status, education, alcohol and calcium intake, and hormone use. Peri-/premenopausal had higher BUA levels (112.39 ± 10.05 dB/MHz) compared to postmenopausal women (106.44 ± 9.95 dB/MHz). In both groups, BUA levels were higher in the fourth compared to the lowest quartile of PA (p for trend < 0.05). In women with BMI < 30, but not BMI ≥ 30 kg/m(2), PA remained positively associated with BUA levels (p for interaction = 0.03). However, when waist circumference higher than 88 cm or body fat percentage (BF%) measures above the median were used to define obesity, a significant positive relationship was also observed in women with BMI < 30 kg/m(2) but with higher waist circumference or BF%. In conclusion, our results strengthen the hypothesis that PA has a positive influence on BUA levels, though dependent on weight.
Keywords: Bone loss; Bone mineral density; Broadband ultrasound attenuation; Obesity; Physical activity.