Lean Mass and Not Fat Mass Is Associated With Male Proximal Femur Strength

Abstract

Obesity is suspected to confer protection against fracture, but evidence is mixed. We examined proximal femur geometry and body composition measures in a diverse group of 1171 men (30-79 yr of age). Analyses showed that nonbone lean mass, but not fat mass, is independently associated with measures of proximal femur density, axial and bending strength, and resistance to buckling. Introduction: Obesity is often said to confer protection against fracture, but the mechanisms driving such an association remain poorly understood. We hypothesized that the effect of increased body mass on bone structure would be accounted for by total and/or appendicular nonbone lean mass, and that once these trends were removed, fat mass would show no protective influence. To test this hypothesis, we examined body composition and geometric indices of proximal femur strength in an ethnically diverse (black, Hispanic, and white) sample of randomly selected men, 30-79 yr of age. Materials and Methods: Data were obtained from N ‫ס‬ 1171 community-dwelling subjects enrolled in the cross-sectional Boston Area Community Health/Bone study. Body composition was obtained by DXA. Hip geometry parameters at the narrow neck, intertrochanter, and shaft were obtained using Hip Structural Analysis of DXA images. These measures included BMD, bone material in cross-sections (cross-sectional area), bending strength (section modulus), and propensity to buckle under compression (average buckling ratio). Analyses controlled for age, race/ethnicity, height, and physical activity. Results: In exploratory analyses, lean mass, fat mass, and BMI were each positively associated with hip strength. However, controlling for lean mass was sufficient to remove the positive, and induce a negative, association for fat mass or BMI. Associations between lean mass and hip strength were strongest and resistant to control for other measures. Lean mass alone was sufficient to account for a substantial proportion of racial/ethnic difference in hip strength measures, whereas fat mass exhibited no comparable explanatory power. Conclusions:The positive association between relative weight and proximal femur strength is accounted for by lean mass, suggesting that, in men, the protective effect of BMI in preventing fracture is mediated not by adipose tissue but by the influence of increased muscle mass accompanying elevated BMI.

Bone cross-sectional geometry in male runners, gymnasts, swimmers and non-athletic controls: a hip-structural analysis study

“…However, although being of smaller stature, gymnasts had greater BMD than all groups, which suggests superiority in bone mineral and strength. Importantly, and in agreement with several previous studies (DiVasta et al, 2007;Travison et al, 2008), total lean body mass was found to be a significant predictor in measures of BMD, CSA, CSMI, and FSI, whereas total body fat percentage was not. Lean body mass is recognised as a surrogate for the muscle loading forces that direct bone adaptation.…”

Multivariate analysis of lifestyle, constitutive and body composition factors influencing bone health in community-dwelling older adults from Madeira, Portugal

“…The multiple regression analyses, revealed that these constitutive and body composition factors make the strongest contribution to explained the dependents variables, when the variance explained by all other variables in the model was controlled for. Specifically, age, TLTM and TFM for FNBMD in both genders and TFM in men and TFM and age in women for LSBMD and FSI, Other studies have shown that age (Hannan et al, 2000), BM (Dargent-Molina et al, 2000;Felson et al, 1993), TLTM (Dytfeld et al, 2011;Ho-Pham et al, 2010;Travison, Araujo, Esche, Beck, & McKinlay 2008) and TFM (Ho-Pham et al, 2010) are important predictors of BMD in older adults males and females, corroborating our findings. Results from multiple regression analysis in our study, showed that age, TLTM and TFM entered as the primary and most significant contributors for FNBMD in our study, accounting for between 13-21.1% and 16.2-36.9% of the explained variation in these measures in males and females, respectively.…”

Obesity and fracture risk

“…Opposite results have also been reported showing that lean mass, not fat mass, is more closely associated with BMD. Still other studies have found that both lean mass and fat mass were significant predictors of BMD, with lean mass being a more important predictor than fat mass in premenopausal women, and fat mass more important than lean mass in postmenopausal women (3,(12)(13)(14). Moreover, Gnudi et al (15) found that the relationship between BMD and body composition is different between women with or without osteoporosis.…”