Fat mass influence on bone mass is mediated by the independent association between lean mass and bone mass among elderly women: A cross-sectional study

ObjectivesTo study the independent association of fat mass (FM) and lean mass (LM) with bone mass and to study the differences in bone mass by weight and fat status in 223 seniors (aged 65–89 years) from the city of Zaragoza (Spain), after controlling for age, height, physical activity (PA) and LM.Study designCross-sectional study.Main outcome measuresLM, FM, bone mineral content (BMC) and density (BMD) were measured with dual energy X-ray absortiometry. The relationships of FM and LM with bone-related variables (subtotal body, hip, femoral neck and lumbar spine) were analyzed by linear regression and differences between weight and fat status were analyzed by one-way analysis of covariance.ResultsIn men, there were no significant associations between FM and BMC or BMD. In women FM was positively associated with bone-related variables after adjustment for age, height and PA, whereas adjustment for LM removed all these significant associations. Overweight/obese elderly women had higher BMC and BMD than their non-overweight peers in all regions studied. Additional adjustment for PA did not change the differences between weight status groups, while adjusting for LM removed some of the associations. Overfat/obese men and women did not show higher levels of bone mass than their non-overfat peers. LM was positively associated with bone variables in both sexes. Additional adjustment for PA and FM did not alter the results.ConclusionThe association between fat mass and bone mass of elderly women is mediated by the independent association between lean mass and bone mass.