Cardiorespiratory fitness is associated with body composition and insulin resistance in European adolescents: HELENA study.

Background: The present study aimed to examine the independent association between cardiorespiratory fitness, sedentary time and insulin resistance in European adolescents.
Methods: A subset (N.=1097) of a large multicenter European study (HELENA-CSS study) was used in the present study. Serum concentrations of glucose (G<inf>F</inf>) and insulin (I<inf>F</inf>) were measured after overnight fast and homeostasis model assessment (HOMA-IR) was calculated. Sedentary time and time spent on moderate-to-vigorous physical activity (MVPA) was objectively measured by accelerometers. Moreover, sedentary activities were self-reported via questionnaires.
Results: Multilevel linear regression analysis revealed that adolescents watching TV≥2 h/day had higher HOMA-IR (P=0.007). Further adjustment for MVPA, showed that watching TV≥2 h/day remained significantly associated with IR (P=0.002). In this model, MVPA was inversely associated with HOMA-IR (P=0.001). Further controlling for waist circumference showed that adolescents watching TV≥2 h/day continued to have higher HOMA-IR levels (P=0.002). Stratified analysis by weight status, revealed that watching TV≥2 h/day was independently associated with HOMA-IR only in normal weight adolescents, while MVPA was inversely associated with HOMA-IR in both overweight/obese and normal weight adolescents. Only the volume of maximum oxygen consumption (VO<inf>2</inf>max) over body fat mass ratio was inversely associated with HOMA-IR after controlling for several confounders.
Conclusions: The present study showed that watching TV≥2 h/day and MVPA were associated with HOMA-IR. However, after controlling for several confounders, only VO<inf>2</inf>max/body fat mass ratio remained negatively associated with HOMA-IR. Future interventions should aim both to promote physical activity and reduce sedentary time in adolescents to improve their cardiorespiratory fitness and postpone the onset of diabetes in adulthood.