Relationship Between Body Composition and Insulin Resistance Evaluated by the TyG Index: A Retrospective Study Among Chinese Population

The triglyceride glucose (TyG) index, a novel and easily obtained marker of insulin resistance (IR), has been shown to predict metabolic diseases. Monitoring body composition is crucial in assessing disease states. This study aimed to investigate the relationship between body composition and IR as assessed by the TyG index. Between January 2018 and December 2021, 12,186 individuals were initially enroled, with 4061 adults were ultimately included. Body composition, including fat mass (FM), fat mass index (FMI), fat-free mass (FFM), fat-free mass index (FFMI), and percent body fat (PBF), was measured using bioelectrical impedance analysis. Spearman analysis assessed correlations between body composition indices and the TyG index. Binary logistic regression identified independent predictors of IR. Older women (≥ 50 years old) showed significantly higher BMI, PBF, FM, FMI, FFMI, HOMA-IR, and the TyG index, but lower FFM compared to younger women; Older men exhibited significantly lower BMI, FM, FFM, FFMI, HOMA-IR, and the TyG index than the younger men. FM, FMI, FFM, FFMI, and PBF were positively correlated with the TyG index. FFMI and PBF significantly predicted IR in both genders. Combined FFMI and PBF yielded an area under the ROC curves of 0.718 in women and 0.661 in men for IR diagnosis. The TyG index correlates with body composition parameters of FFMI and PBF as well as HOMA-IR potentially making it a convenient marker of metabolic risk.