The relationship between body composition and bone mineral content: threshold effects in a racially and ethnically diverse group of men.
We examined BMC and body composition in 1,209 black, Hispanic, and white men. Weight, BMI, waist circumference, and fat mass were associated with BMC only up to certain thresholds, whereas lean mass exhibited more consistent associations. The protective influence of increased weight appears to be driven by lean mass.


BACKGROUND
Reduced body size is associated with decreased bone mass and increased fracture risk, but associations in men and racially/ethnically diverse populations remain understudied. We examined bone mineral content (BMC) at the hip, spine, and forearm as a function of body weight, body mass index (BMI), waist circumference, fat mass (FM), and nonbone lean mass (LM).


METHODS
The design was cross-sectional; 363 non-Hispanic black, 397 Hispanic, and 449 non-Hispanic white residents of greater Boston participated (N = 1,209, ages 30-79 y). BMC, LM, and FM were measured by DXA. Multiple linear regression was used to describe associations.


RESULTS
Weight, BMI, waist circumference, and FM were associated with BMC only up to certain thresholds. LM, by contrast, displayed strong and consistent associations; in multivariate models, femoral neck BMC exhibited a 13% increase per 10 kg cross-sectional increase in LM. In models controlling for LM, positive associations between BMC and other body composition measures were eliminated. Results did not vary by race/ethnicity.


CONCLUSIONS
The protective effect of increased body size in maintaining bone mass is likely due to the influence of lean tissue. These results suggest that maintenance of lean mass is the most promising strategy in maintaining bone health with advancing age.
New England Research Institutes, Watertown, MA 02472, USA. ttravison@neriscience.com
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D000328:Adult; D000368:Aged; D044383:Black People; D001823:Body Composition / Q000502:physiology*; D015519:Bone Density / Q000502:physiology*; D001900:Boston; D003430:Cross-Sectional Studies; D005272:Femur Neck / Q000737:chemistry; D006630:Hispanic or Latino; D006801:Humans; D008159:Lumbar Vertebrae / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D011884:Radius / Q000737:chemistry; D044465:White People; D001741:Black or African American