Abstract
BACKGROUND: The interplay between skeletal muscle loss and excess adiposity has been associated with metabolic dysfunction and may impose a dual burden on physiological homeostasis. This study aimed to investigate the associations of the skeletal muscle mass to visceral fat area ratio (SVR) with metabolically healthy obesity (MHO) and metabolically unhealthy non-obesity (MUNO). METHODS: Data from the 2011–2018 NHANES were analyzed. Obesity phenotypes were defined using body mass index (BMI ≥ 30 kg/m(2)), in combination with the presence of metabolic syndrome components. Associations of SVR with MHO and MUNO were assessed using multivariable logistic regression and restricted cubic spline (RCS) analyses. Discriminatory performance was evaluated by area under the curve (AUC) values from receiver operating characteristic (ROC) analyses, comparing SVR with other anthropometric and body composition measures. Subgroup analyses were conducted to evaluate potential effect modification, and sensitivity analyses were performed to assess the robustness of the findings. RESULTS: Among 4,609 adults, 5.06% were classified as MHO and 39.97% as MUNO. After covariate adjustment, higher SVR was associated with greater odds of MHO (OR = 1.48; 95% CI: 1.16–1.89) and lower odds of MUNO (OR = 0.47; 95% CI: 0.37–0.60). RCS analyses suggested linear associations for MHO and MUNO. Subgroup analyses suggested stronger associations for MHO among current or former drinkers, and for MUNO among men and adults aged 45–59 years. ROC analyses showed modest discriminatory performance, with AUC values of 0.65 for MHO and 0.71 for MUNO. CONCLUSIONS: SVR was associated with both MHO and MUNO. These findings suggest that SVR may provide supplementary information for characterizing obesity phenotypes, but its clinical relevance remains uncertain and requires further confirmation in longitudinal and interventional studies. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12944-025-02744-x.