Are associations between physical activity and lipoproteins in children moderated by fitness and fatness?

It is not known whether aerobic capacity (fitness) or overweight/obesity (fatness) moderate the association between physical activity (PA) and lipoproteins/lipids in children. The aim of this study was to investigate moderation of the cross-sectional and longitudinal associations between PA and the lipoprotein subclass profile by fitness and fatness in children. Eight hundred and sixty-two (cross-sectional analysis) or 787 (longitudinal analysis) children (age 10.2 years; body mass index 18.0; 49% girls) provided data on PA (ActiGraph GT3X+), the Andersen aerobic fitness test, and waist-to-height ratio at baseline, and lipoprotein particle concentrations, sizes and lipids (nuclear magnetic resonance spectroscopy) at baseline and 7-month follow-up. Associations for the PA intensity spectrum with a lipoprotein score were analysed by quartiles of baseline fitness and fatness using multivariate pattern analysis. Explained variances for the associations between PA and the lipoprotein score were 2.32-6.99% for children having low fitness or high fatness, adjusted for covariates. In these subgroups, PA was associated with a less atherogenic lipoprotein profile and sedentary time with a more atherogenic lipoprotein profile. No associations were found in more favourable fitness or fatness subgroups. Our findings suggest that PA can mitigate the increased risk of cardiovascular disease among children with low fitness and/or high fatness levels.