Background: The magnitude of effects of lean mass and fat mass on bone health is controversial, and this study is a contribution to understand its effects on skeletal composition.
Aim: We explored the relationship of body fat and muscle parameters with bone mineral density (BMD) and age and observed if it changed when matched with body mass index (BMI) of the same study subjects.
Methods: One-hundred sixty-four community dwelling, ambulatory elderly attending the osteoporosis services of a Dublin hospital was recruited. Out of these, 158 female patients had a total body DXA scan, and their body composition outcomes were included in this analysis. The relationship between body fat and muscle composition and BMD at all sites was determined and also matched by BMI.
Results: Total-Body BMD had a strong positive correlation with lean mass(r = 0.492, p 0.00) and fat mass(r = 0.414, p 0.00), though lean mass remained the strongest predictor of BMD at all sites. Increasing BMI categorically had a positive effect on both lean mass and fat mass. Increasing age was significantly associated with an increase in fat mass(r = 2.40, p 0.00) and a decrease in muscle mass(r = 0.478, p 0.01).
Conclusion: Both lean mass and fat mass are significant predictors of BMD. To preserve BMD maintenance or increase of lean mass is more effective than fat mass. BMI correlates well with body composition; however, we recommend the use of direct measures of body fat and muscle to make this relation more interpretable. Total Body DXA is a readily available diagnostic tool which provides high-valued information about body composition.
Keywords: BMI; Body composition; Fat mass; Lean mass; Osteoporosis; Total body DXA.