ORIGINAL RESEARCH article
Front. Nutr.
Sec. Nutrition and Metabolism
Volume 12 - 2025 | doi: 10.3389/fnut.2025.1597065
Nonlinear Associations and Threshold Effects of BRI, CI, WHtR with Grip Strength in U.S. Adults Aged ≥20: A Cross-sectional Study
Provisionally accepted
- Zhuhai People's Hospital, Zhuhai, China
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AbstractBackground: Muscle strength is strongly linked to various physiological functions and health risks, with grip strength serving as a key indicator for its assessment.Currently, the relationship between novel obesity indices (Body Roundness Index (BRI), Conicity Index (CI), Waist-to-Height Ratio (WHtR) and muscle strength remains unclear. The purpose of this study was to investigate the nonlinear/threshold relationships between BRI, CI, WHtR and grip strength. Methods:A cross-sectional study design was adopted to analyze the data of 9,356 participants from the National Health and Nutrition Examination Survey (NHANES) conducted between 2011 and 2014. The researchers measured grip strength and calculated BRI, CI, and WHtR, while controlling for age, gender, race, and other covariates.Statistical analyses included linear regression, smooth curve fitting, and threshold effect models to evaluate nonlinear/threshold relationships. The significance level was set at P<0.05, and 95% confidence intervals (CIs) were reported.Results: BRI, CI, and WHtR exhibited significant nonlinear associations with grip strength. For BRI, values below 3.55 showed a strong positive effect (β=3.60, 95% CI: 2.81–4.39), with weakened but persistent positive effects above this threshold (β=0.24, 95% CI: 0.10–0.39). WHtR demonstrated a similar pattern, with a threshold at 0.51: β=62.46 (48.36–76.55) below and β=6.47 (2.85–10.08, ) above. CI showed an inverted U-shaped relationship, shifting from positive (β=15.87, 7.85–23.90, ) to negative (β=−9.98, −14.98 to −4.98, p<0.01) at a threshold of 1.27.Conclusion: In U.S. adults, BRI，CI and WHtR exhibit nonlinear and threshold-dependent associations with grip strength, suggesting these indices can refine the assessment of muscle strength. Findings indicate that integrating these indices may enhance the accuracy of risk stratification for muscle dysfunction, particularly in individuals with central obesity. Longitudinal studies are needed to further validate the causal relationships underlying these associations.
Keywords: Cross-sectional study, Body measures, Obesity, NHANES, Muscle Strength
Received: 20 Mar 2025; Accepted: 26 May 2025.
Copyright: © 2025 Wu, Liao, Yang and Zhang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: JIANCHAO Wu, Zhuhai People's Hospital, Zhuhai, China
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