Changes in Cardiorespiratory Fitness Predict Changes in Body Composition From Childhood to Adolescence: Findings From the European Youth Heart Study

Background: Several variables, such as waist circumference (WC) and trunk skinfolds (TS), are indicators of body fat. There is interest in evaluating the effect of cardiorespiratory fitness (CRF) measures on changes in these markers from childhood to adolescence. Purpose: To examine CRF as a potential predictor of changes in body fat over an 8-year follow-up period in a pediatric population. Methods: A cohort study of 86 children (44 girls, 42 boys) with a mean age of 9.8 +/- 0.3 years who participated in the Portuguese arm of the European Youth Heart Study in 2000 completed a follow-up evaluation in 2008 at a mean age of 17.0 +/- 0.4 years. Cardiorespiratory fitness, expressed as maximal oxygen consumption (VO2 max) (mL.kg(-1).min(-1)), was assessed during an incremental multistage bicycle test to exhaustion. Physical activity (PA) was objectively measured by accelerometry at both periods of evaluation. Fat mass (FM) was assessed using anthropometric models, sum of TS, and WC. Changes were expressed as a percentage of the baseline value. Comparison of means and linear regression analysis were used for data analysis. Results: While CRF significantly increased among boys (P < 0.05) and decreased in girls (P < 0.01), the percentage of body fat decreased over time in boys (P < 0.01) and increased among girls. Alone, CRF explained 39%, 26%, and 25% of the total variance in WC, FM, and TS, respectively (P < 0.01). Adjusting for PA, sex, and maturation changes, CRF remained a significant predictor of WC (beta = -0.335; P < 0.01), FM (beta = -2.084; P < 0.01), and TS (beta = -1.500; P < 0.01). Conclusion: Changes in CRF are a significant predictor of changes in body fat percentage from childhood to adolescence. School-based PA interventions are encouraged to maintain or improve CRF from childhood and throughout adolescence to prevent increased percentages of body fat, particularly in the abdominal region.