Soft tissue body composition: familial resemblance and independent influences on bone mineral density.

Familial resemblance in fat and lean soft tissue and the influence of these body composition measures on bone mineral density (BMD) were determined in 162 adult members of 42 families. Whole body fat and lean mass and BMD of the spine and femoral neck were measured by dual-energy X-ray absorptiometry and BMD of the heel and radius by single-photon absorptiometry. Significant correlations of lean tissue were observed between mothers and daughters (r = 0.35, p < 0.05), fathers and sons (r = 0.36, p < 0.05), and daughters and sons (r - 0.42, p < 0.01) after adjustment for age, height, fat mass, physical activity, and parity (among women). Fat tissue was not significantly correlated among any family member pairs. Lean tissue, but not fat, was positively associated with BMD in one or more family member subgroups at all skeletal sites. These findings suggest a hereditary component to muscle mass. Previously documented familial similarities in bone density may be related in part to the influence of lean mass on bone density.