Context: Fat and muscle are linked to bone metabolism.
Objective: The objective of the study was to investigate the association of fat mass (FM) and lean mass (LM) with bone mineral density (BMD) according to gender and age.
Design and setting: This was a population-based, cross-sectional study from Korea National Health and Nutrition Examination Surveys.
Participants: 15,036 Koreans (6692 men and 8344 women) aged 10-95 years.
Main outcome measures: BMD and body compositions were measured using dual-energy X-ray absorptiometry. BMD was determined at the femoral neck, total hip, and lumbar spine. Body compositions included total FM (TFM), percentage FM (PFM), truncal FM (TrFM), total LM (TLM), and appendicular skeletal muscle mass/weight (ASM/Wt).
Results: We categorized each man and woman into one of three age groups, based on changes in age-related BMD and the hormonal status. In all gender and age groups, TFM, PFM, and TrFM associated inversely with BMD (P < .001-.034), whereas TLM and ASM/Wt associated positively (P < .001-.037) after adjusting for confounders. The negative contribution of FM (P < .001-.034), and the positive contribution of LM (P < .001-.035) on BMD were significantly stronger in men than in women. The associations were strongest in men of growing age (P = .003-.040). When we subdivided the subjects into four groups based on the median values of PFM and TLM, FM had a greater effect than LM on BMD in men (P < .001-.006).
Conclusion: These results demonstrate that the effects of FM and LM on BMD may be based on gender and age.