The association between basal metabolic rate and bone mineral content: the mediating role of inorganic salts

This study explored the correlation between basal metabolic rate (BMR) and bone mineral content (BMC) in middle-aged and elderly people, and verified inorganic salts act as mediators linking BMR and BMC. This prospective cross-sectional study enrolled 609 subjects aged ≥ 40 years from 2025 to 2026. Ultrasonic bone densitometer was used to test BMC, osteo index (OI), Z and T scores; a body composition analyzer measured BMR and inorganic salt levels. SPSS 26.0 was applied for univariate, multivariate regression, mediation and gender-stratified analyses (378 females, 231 males), with P < 0.05 as the significance threshold. After covariate adjustment, BMR showed independent positive correlations with BMC and inorganic salts (all P < 0.001); inorganic salts also positively predicted BMC independently ( P < 0.001). The results of the mediation test in the statistical analysis indicated that inorganic salts had a significant masking mediation effect: the total effect of BMR on BMC was positive ( β = 0.0024, 95% CI 0.0023–0.0025), direct effect negative ( β =− 0.0005, 95%CI −0.0006 to −0.0005), and indirect effect positive ( β = 0.0030, 95% CI 0.0028–0.0031, all P < 0.001). Gender stratification yielded consistent masking mediation results for both sexes. Univariate analysis found BMR negatively correlated with OI, Z-score and T-score in men ( P < 0.5), yet all associations vanished after adjustment; no such correlations existed in females. Among middle-aged and elderly individuals, BMR showed a positive statistical association with BMC, with inorganic salts demonstrating a statistical mediating role in this cross-sectional relation. This statistical pattern reflects correlated changes across the three variables. These observational results provide directions for future research on osteoporosis.