Obesity and physical fitness of pre-adolescent children during the academic year and the summer period: effects of organized physical activity.

This study examined obesity and parameters of physical fitness in 178 elementary schoolchildren during an academic year as well as after the summer holidays. Results showed significant physical fitness improvements during the school year, with little or no changes in the summer holidays. Children who reported less than 30 minutes of daily participation in physical activity demonstrated lower prevalence rates for overweight and obesity as well as superior fitness performance. The detrimental effect of the summer break on the progress of physical fitness was less in children who did participate in physical activity than in those who did not. Longitudinal modelling using generalized estimating equations demonstrated that physical activity is a major contributing factor for obesity over time, masking the singular effect of various fitness parameters. It is concluded that pre-adolescent children advance in physical fitness mainly during the school year, with physical activity being a beneficial countermeasure for the development of obesity.