Relationship between body mass index, insulin resistance, and metabolic syndrome in children: Effect of vigorous physical activity.

The association between physical activity (PA), obesity, insulin resistance (IR), and metabolic syndrome (MetS) in pediatric populations remains unclear. This cross-sectional study investigated 1) whether IR mediates the relationship between obesity and MetS in Korean children, and 2) whether PA intensity modulates the effect of obesity on IR. Six hundred and thirteen Korean children (320 boys/293 girls) aged 9-12 years participated in this study. Mediation analysis showed that body mass index (BMI) z-scores influence MetS directly in boys (β = 2.151, SE = .781, p = .040) and girls (β = 7.531, SE = 1.929, p = .040). A 5000 bootstrapping for an indirect effect confirmed that the homeostatic model assessment for IR (HOMA-IR) mediates the relationship between BMI z-scores and MetS in both boys (β = .544, standard error, SE = .325, 95% confidence interval, 95% CI [0.121, 1.399]) and girls (β = .865, SE = 3.748, 95% CI [0.459, 2.446]). Finally, our moderated-mediation analysis showed a significant interaction effect between BMI z-scores and vigorous PA on HOMA-IR (β = .002, SE = .001, p = .023) in boys only. This indicates that vigorous PA influences the relationship between BMI z-scores and HOMA-IR in boys.