Triglyceride-Glucose Index and Its Relation to Metabolic Syndrome and Physical Fitness in Children

Background: Triglyceride-glucose (TyG) index and its relationship with metabolic syndrome (MetS), physical activity (PA), and physical fitness in the pediatric population remain unclear. This cross-sectional study explored the mediating effect of central obesity and PA on the relationship between the TyG index and physical fitness in a pediatric population. Methods: A total of 614 Korean children (320 boys and 294 girls) aged 7-12 years participated in this study. MetS was defined as the continuous MetS risk value in the 4th quartile obtained by adding standardized scores for the syndrome components. PA was quantified using an accelerometer, and physical fitness was evaluated using composite scores for the endurance, strength, power, and flexibility domains. Results: Receiver operating characteristic curve analysis revealed that the TyG index outperformed body mass index (z = 3.005, P = 0.003) and the homeostasis assessment model for insulin resistance (z = 3.543, P = 0.001) in detecting the presence of MetS. Mediation analysis revealed that while the TyG index has a direct effect on composite physical fitness scores (β = -0.3832 and SE = -2.0942, 95% confidence interval, CI = -0.7426 to -0.0239), there was an indirect effect of the TyG index on physical fitness via vigorous PA (β = -0.0802 and SE = 0.0377) and waist-to-hip ratio (β = -0.1318, SE = 0.0509). Conclusion: The TyG index has a significant impact on physical fitness in the presence of the two mediators (β = $-$0.3832, SE = -2.0942, 95% CI = -0.7426 to $-$0.0239).