Work

Independent association between relative fat mass and total bone mineral density in U.S. adolescents: a cross-sectional study adjusting for Appendicular Lean Mass Index

Year: 2026

Type: article

Abstract: The relationship between adiposity and bone health, often referred to as the “obesity paradox,” remains a subject of debate. Relative fat mass (RFM) has recently emerged as a more accurate surrogate for body fat percentage than the Body Mass Index (BMI). However, the independent association between RFM and bone mineral density (BMD) in the adolescent population, particularly after rigorously accounting for lean mass, remains ambiguous, particularly concerning the independent metabolic influence of adiposity. This cross-sectional study evaluated 3,933 adolescents (aged 12–19 years) from the 2011–2018 National Health and Nutrition Examination Survey (NHANES). Multiple imputation was applied to manage missing covariates. We employed weighted multivariate linear regression to assess the association between RFM and total BMD. Appendicular Lean Mass Index (ALMI) was integrated as a core covariate to isolate the metabolic influence of adiposity from its mechanical loading effects. In the unadjusted model, RFM showed no significant correlation with total BMD (β = 0.001, P = 0.122). However, after adjusting for ALMI and other potential confounders, a significant negative association emerged. In the fully adjusted model, each one-unit increase in RFM was associated with a 0.005 g/cm 2 decrease in total BMD (β = -0.005, P < 0.001). Furthermore, sex-specific non-linear relationships were identified. Threshold effect analysis revealed inflection points at an RFM of 21.28 for males and 39.44 for females. Beyond these respective thresholds, the decline in bone mineral accrual significantly accelerated ( P < 0.001). After accounting for the mechanical loading effects of ALMI, higher RFM is independently associated with reduced total BMD in adolescents. These findings reveal observational sex-specific inflection points (21.28 for males, 39.44 for females) beyond which lower BMD was observed. These thresholds should be interpreted as exploratory rather than clinically actionable targets.

Source: Scientific Reports

DOI: 10.1038/s41598-026-52209-z

Authors: Penghui Lv, Chenglong Zhang, Shuaiwei Wei, Jincheng Bai, Lu Li, Jianjun Chang

Institutions: Shanxi Medical University, Shanxi Academy of Medical Sciences

Language: English

Topic: Bone health and osteoporosis research

Subfield: Orthopedics and Sports Medicine

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: gold

Estimated APC paid: $2,690