Predicting insulin resistance in non-diabetics: Comparing obesity indicators using machine learning

This cross-sectional study aimed to compare obesity indicators for predicting insulin resistance using machine learning. Data were obtained from NHANES 2015 to 2018, focusing on a nondiabetic adult population. Insulin resistance was defined as HOMA-IR ≥ 75th percentile of the training set. Key predictors were selected via bootstrap stability selection with elastic net. Logistic regression, random forest, and extreme gradient boosting (XGBoost) models were built using body mass index (BMI) and waist-to-height ratio (WHtR). Performance was assessed by area under the curve (AUC), sensitivity, specificity, accuracy, calibration, and decision curve analysis. Race-stratified and nested regression analyses were performed. A total of 3562 subjects were included. BMI, WHtR, Glycated hemoglobin, and triglycerides were identified as key predictors. All models achieved AUC > 0.79; logistic regression (LR) performed best (BMI-based LR: AUC = 0.811; WHtR-based LR: AUC = 0.811). WHtR-based LR showed slightly better accuracy (0.746 vs 0.715) and specificity (0.744 vs 0.678). Obesity indicators had the highest feature importance, and race-stratified analyses confirmed general robustness across subgroups. WHtR and BMI are strong independent predictors of IR. LR models using these simple indices performed well in discrimination, calibration, and net benefit, offering cost-effective screening options, particularly where resources are scarce. Future work should prioritize external validation and race-specific thresholds.