ORIGINAL ARTICLE Association between fat mass, lean mass, and bone loss: the Dubbo osteoporosis epidemiology study S. Yang & J. R. Center & J. A. Eisman & T. V. Nguyen Received: 6 August 2014 /Accepted: 15 December 2014 # International Osteoporosis Foundation and National Osteoporosis Foundation 2014 Abstract Summary Lower body fat mass is a risk factor for bone loss at lumbar spine in postmenopausal women, but not in men. Body lean mass and fat mass were not associated with femoral neck bone loss in either gender. Introduction Bone density and body mass are closely associ- ated. Whole body lean mass (LM) and fat mass (FM) together account for approximately 95 % of body mass. Bone loss is associated with loss of body mass but which of the compo- nents of body mass (FM or LM) is related to bone loss is not well understood. Therefore, in this study, we sought to assess whether baseline FM or LM has predictive value for future relative rate of bone mineral density (BMD) changes (%/year). Methods The present population-based cohort study was part of the ongoing Dubbo Osteoporosis Epidemiology Study (DOES). BMD, FM, and LM were measured with dual energy X-ray absorptiometry (GE-LUNAR Corp, Madison, WI). BMD measurements were taken in approximately every 2 years between 2000 and 2010. We only included the partici- pants with at least two BMD measurements at the femoral neck and lumbar spine. In total, 717 individuals (204 men and 513 women) aged 50 years or older were studied. Results Rate of bone loss at femoral neck and lumbar spine was faster in women than in men (all P <0.01). In bivariable regression analysis, each 5 kg greater FM in women was associated with 0.4 %/year (P =0.003) lower bone loss at lumbar spine. This magnitude of association remained virtu- ally unchanged after adjusting for LM and/or other covariates (P =0.03). After adjusting for covariates, variation of FM accounted for ∼1.5 % total variation in lumbar spine bone loss. However, there was no significant association between FM and change in femoral neck BMD in either men or women. Conclusion Lower FM was an independent but modest risk factor for greater bone loss at the lumbar spine in women but not in men. If further studies confirm our findings, FM can help predict lumbar spine bone loss in women. Keywords Body composition . Bone loss . Fat mass . Lean mass . Osteoporosis Introduction Bone loss and its consequent osteoporosis collectively is a silent health problem in elderly men and postmenopausal women. Bone loss takes place when bone resorption becomes more active than bone formation. When bone mineral density (BMD) declines to the cut-off of a T-score< -2.5, it meets the WHO definition of osteoporosis [1]. Approximately 20 years ago, it was shown that bone loss progressively increased with advancing age [2], and that women tended to lose more bone than men [3], and this finding was subsequently observed in other populations [4]. Excessive bone loss is associated with S. Yang : J. R. Center : J. A. Eisman : T. V. Nguyen (*) Osteoporosis and Bone Biology Research Program, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW 2010, Australia e-mail: t.nguyen@garvan.org.au J. R. Center : J. A. Eisman Department of Endocrinology, St Vincent’ s Hospital, Sydney, Australia J. A. Eisman School of Medicine, The University of Notre Dame Australia, Fremantle, Australia T. V. Nguyen School of Public Health & Community Medicine, Faculty of Medicine, University of New South Wales, Sydney, Australia T. V. Nguyen Centre for Health Technologies, University of Technology, Sydney, Australia Osteoporos Int DOI 10.1007/s00198-014-3009-6