Association between cardiorespiratory fitness (CRF) and insulin resistance (IR) in obese adolescents has been insufficiently studied. The aim of our prospective, cross-sectional study was to investigate the association between CRF and IR in 200 pubertal adolescents who had been referred to a tertiary care center due to obesity. According to body mass index (BMI), adolescents were classified as mildly or severely obese. Homeostatic model assessment of insulin resistance (HOMA-IR) was calculated. Maximal oxygen uptake (VO2max) was determined from submaximal treadmill exercise test. CRF was categorised as poor, intermediate or good, according to VO2max terciles. One-way analysis of variance (ANOVA) revealed a significant main effect of CRF on HOMA-IR. Subsequent analyzes showed that obese adolescents with poor CRF had higher HOMA-IR than obese adolescents with good CRF. Two-way ANOVA with Bonferroni correction confirmed significant effect of interaction of CRF level and obesity class on HOMA-IR. Severely obese adolescents had higher HOMA-IR than mildly obese, with either good or poor CRF. However, HOMA-IR did not differ between severely obese adolescents with good and mildly obese adolescents with poor CRF. In conclusion, CRF is important determinant of IR in obese adolescents, regardless of obesity class. Therefore, CRF assessment should be a part of diagnostic procedure, and its' improvement should be a therapeutic goal.

Lavinia La Grasta Saboli? has completed her PhD at University of Zagreb, Faculty of kinesiology. She is the head of Department of pediatric endocrinology and diabetology, at University Hospital Center Sestre milosrdnice, Zagreb, Croatia. Her areas of interest are obesity and diabetes. She has over 20 publications, that have been cited over 100 times. She is also author of several chapters in textbooks and university manuals.