Background: The aim of this study was to investigate the influence of body mass index, body weight, lean mass, fat mass, and basal energy expenditure on bone mineral density in postmenopausal women.
Methods: This was a cross-sectional, descriptive study of a sample of 50 women, with minimum time since menopause between 1 and 10 years. Bone mineral density was assessed at the lumbar spine (L2-L4), femoral neck, Ward's triangle, and trochanter using dual-energy X-ray absorptiometry. Body mass index, lean mass, fat mass, and basal energy expenditure were measured by bioimpedance.
Results: The mean age of the women was 51.49 ± 3.86 years and time since menopause was 3.50 ± 2.59 years. Significant negative correlations were found between chronological age and lumbar spine, femoral neck, Ward's triangle, and trochanteric bone mineral density. In regard to time since menopause, we also observed significant negative correlations with bone mineral density at the lumbar spine and Ward's triangle. The following significant positive correlations were recorded: body mass index with bone mineral density at the femoral neck and trochanter; fat mass with bone mineral density at the femoral neck and trochanter; lean mass with bone mineral density at the lumbar spine, femoral neck, and trochanter; and basal energy expenditure with bone mineral density at all sites assessed. On the other hand, the multiple linear regression model showed that: 20.2% of bone mineral density variability at the lumbar spine is related to lean mass and time since menopause; 22.3% of bone mineral density variability at the femoral neck is related to body weight and age; 18.9% of bone mineral density variability at Ward's triangle is related to age and basal energy expenditure; and 39% of bone mineral density variability at the trochanter is related to body mass index, age, and menarche.
Conclusion: Changes in bone mineral density, specific for each skeletal site, are influenced by age, time since menopause, body weight, body mass index, lean mass, and basal energy expenditure. Lean mass and basal energy expenditure positively influenced bone mineral density at the lumbar spine and Ward's triangle, with a predominance of trabecular bone.
Keywords: body composition; bone mineral density; energy expenditure; menopause; women.