Association Between Cardiorespiratory Fitness And Fatness In 10-16 Year Old Brazilian School Adolescents

Abstract

BACKGROUND: Cardiorespiratory fitness (CRF) is one of the most important health markers and predictor of morbidity and mortality from chronic diseases. Low levels of CRF seem to contribute to the development of obesity and cardiovascular diseases across different age groups, including children and adolescents. PURPOSE: To analyze the association between CRF and body fat percentage (BF%) among a sample of adolescents in Brazil. METHODS: This cross-sectional school-based study was conducted on 244 students (123 of whom boys) with 10 to 16 years old (13.3±1.5), from the Bradesco Foundation School (Campinas - Sao Paulo, Brazil). BF% was measured by bioelectrical impedance analysis (BIA) and dichotomized into ‘normal’ and ‘increased risk’ (Girls: BF%>30 and Boys: BF%>25), according to Willians et al. (1992). Results from shuttle run test proposed by Léger et al. (1988) were used as a CRF marker and the participants were classified as ‘health risk’ and ‘healthy fitness zone’ (Welk et al., 2011). Physical activity level was obtained by the Youth RBS Questionnaire (2005). Descriptive analysis, Spearman Correlation and Binary logistic regression were used. The study was approved by Committee of Ethics in Research of the Faculty of Medical Sciences, University of Campinas (No. 797/2008; CAAE: 3540.0.000.146-08). RESULTS: Mean values of BF% were 20.7±7.0% and 25.6±6.4% for boys and girls, respectively, boys demonstrated higher values of CRF (43.6±5.2ml/kg/min vs 39.7±3.2ml/kg/min) than girls (p<0.01). BF% was negatively correlated with CRF (r = -0.61, p<0.01). Binary logistic regression analysis, after adjustment for age and physical activity level, found that for each unit of decrease in CRF (ml/kg/min) the risk of elevated BF% increases by 31% (95%IC: 0.60-0.80) in boys and 29% (95%IC: 0.58-0.87) in girls, and also that a rise of one percentage point in BF% increases 16% and 15% (p<0.01) the risk of inadequate levels of CRF, in boys and girls, respectively. CONCLUSION: We conclude that CRF is independently associated with the risk of elevated BF% in this sample, as well as the rise of BF% increases the risk of inadequate levels of CRF. Prospective studies and interventions are needed to analyze the causality of these associations.