Assessment of the effects of whole-body muscle and fat mass on bone mineral content based on 628 DXA datasets

Background The prevalence of osteoporosis is steadily increasing. Although the relationships between muscle mass, fat mass, and bone mineral content (BMC) have been extensively studied, they remain contentious. This study aimed to develop a unified statistical model to evaluate the independent effects of total muscle and fat mass on BMC, clarify their respective roles in osteoporosis pathogenesis, and inform targeted prevention strategies. Methods We retrospectively analyzed data from 628 subjects who underwent body composition assessment at the Affiliated Hospital of Nanjing University of Chinese Medicine between January 2022 and July 2024. Collected parameters included age, height, weight, body mass index (BMI), total BMC, total muscle mass, total fat mass, and whole-body bone mineral density (BMD) T-scores. Groups were compared by sex, age and whole-body BMD T-score categories. Spearman correlation and multiple linear regression analyses were used to assess the associations of total BMC with total muscle and total fat mass. Results Males had greater height, weight, BMI, total BMC, total muscle mass, and whole-body T-scores than females ( P < 0.001), while females had higher total fat mass. Total muscle mass consistently showed a stronger positive correlation with total BMC than total fat mass across all subgroups. Multiple linear regression analysis confirmed total muscle mass was the strongest and stable independent positive correlate of total BMC(overall sample β= 0.687, P < 0.001). Total fat mass was positively associated with total BMC only in females, individuals >70 years, and osteoporosis patients, not in normal/osteopenic groups. Age negatively correlated with total BMC, especially in females ( β= -0.395, P < 0.001). BMI correlated with lower total BMC in the total sample, females, and osteopenia group. Conclusions Muscle mass is the strongest and most consistent correlate of BMC. The role of fat is context-specific, varying by sex, age, and bone health. Based on current associative evidence, maintaining muscle may be considered a priority in bone health management, while fat’s impact requires individualized assessment. Clinical Trial Registration http://www.chictr.org.cn/ identifier ChiCTR2400085209.