Is Measuring BMI and Waist Circumference as Good in Assessing Insulin Resistance as Using Bioelectrical Impedance to Measure Total Body Fat and Visceral Fat?

Background: Insulin resistance (IR) is a metabolic disorder linked to type 2 diabetes and cardiovascular diseases. Visceral fat is a better predictor of IR than BMI and waist circumference due to its metabolic and inflammatory impact. Methods such as DEXA and bioimpedance (BIA) estimate body fat, while scales such as METS-IR, SPISE, and TyG assess IR risk. This study analyzes the utility of visceral and body fat measured by BIA compared to other indicators. Methods: A cross-sectional study was conducted on 8590 workers in the Balearic Islands, analyzing anthropometric, clinical, and analytical variables. Body fat and visceral fat were measured by bioimpedance, and insulin resistance was assessed using METS-IR, SPISE, and TyG. ROC curves were used to evaluate the predictive value of BMI, WC, and body fat. Results: The areas under the curve (AUCs) were highest for high METS-IR, particularly in women (>0.97), indicating excellent performance. TyG showed the lowest AUC, especially in men. Body and visceral fat showed the highest AUC for all IR scales. Youden’s indices were highest for high METS-IR, with good predictive capacity, while TyG showed low values, limiting its utility in predicting insulin resistance. Conclusions: Measuring body and visceral fat by BIA is superior to BMI or WC for estimating IR risk.