14th May 2023

Introduction: The prevalence of obesity in children and adolescents grows rapidly. WHO advocates that young people, under the age of 18, should practice at least 60 minutes of MVPA a day, and says that additional time brings even more health benefits, improving muscle and cardiorespiratory fitness, bone health, metabolic and cardiovascular markers. The aim of our work is to estimate the effects of replacing the minutes needed to accomplish 60 minutes/day of moderate to vigorous physical activity, from sedentary behavior time, on health markers, using the isotemporal substitution method.

Method: A sample of 285 Portuguese children and adolescents was categorized in two groups based on body fat percentage. The daily mean moderate to vigorous physical activity was determined using accelerometry. Capillary blood samples and blood pressure were obtained using standard procedures. Data were analyzed by isotemporal substitution analyses estimating the effect of reallocating, from sedentary behavior, the time needed to accomplish 60 minutes of moderate to vigorous physical activity, on health markers.

Results: The replacement of sedentary behavior with moderate to vigorous physical activity reduced the percentage of body fat (B= 2,57; 95%IC: 1,93-3,22), and improved cardiorespiratory fitness in both groups, normoponderal (B= 2,13 ; 95%IC: 1,52-2,74), overweight (B= 2,05; 95%IC 0,74-3,36).

Conclusion: Adding the extra time needed to accomplish the 60 min/day moderate to vigorous physical activity recommendation seems to favorably affect the body composition and cardiorespiratory fitness in normoponderal and overweight children and adolescents.

Acknowledgements: FCT-FCT/UIDB/00617/2020 and LA/P/0064/2020