Effects of sedentary activity and physical activity on bone mineral density and fat in America: National Health and Nutrition Examination Survey, 2011–2018

Summary: We compared the relationship between sedentary activity (SA) and physical activity (PA) with bone mineral density (BMD) and body fat percentage in the United States and found a negative association between SA and BMD and a positive association with body fat percentage. a positive association between PA and BMD and a negative association with body fat percentage. Introduction: SA and PA are associated with changes in skeletal parameters and body fat percentage, and we aimed to investigate and compare the relationship between SA, PA and bone mineral density (BMD) and body fat percentage in men and women. Methods: We assessed the relationship between SA, PA and BMD and body fat percentage in 9249 Americans aged 20-80 years (mean age 38.26 ± 11.39 years) from NHANES 2011-2018.BMD and body fat percentage were measured by dual-energy X-ray bone densitometry (DXA). We used multiple linear regression models to examine the relationships between SA, PA and total BMD and total body fat percentage, adjusted for a large number of confounding factors. Results: After adjusting for race/ethnicity, age, alcohol and smoking behavior, body mass index (BMI), total protein, blood calcium, blood uric acid, cholesterol, blood phosphorus, and blood urea nitrogen, SA was negatively associated with total BMD (β =-0.002 95% CI: -0. 003-0.001, P < 0.001) and SA was positively associated with total lipid percentage (β =0.149 95% CI: 0.111-0.186, P < 0.001). There was a positive correlation between multiple PAs and BMD and a negative correlation between multiple PAs and percent body fat. Conclusions: Our results show that physical activity is a key component of maintaining bone health in both men and women and is strongly associated with lower body fat percentages. Sedentary activity has deleterious effects on skeletal homeostasis and is strongly associated with increased body fat percentage. Healthcare policymakers should advise people to be less sedentary and more physically active in the prevention of osteoporosis and obesity.