Abstract
BackgroundIt is not clear how physical activity affects body composition in adolescents. Physical activity levels are often reduced during this period, and the relative proportion of body fat mass and lean mass undergo natural changes in growing adolescents. We aimed to examine whether self-reported physical activity in leisure time at baseline or change in activity during follow-up affect changes in four measures of body composition; body mass index (kg/m2), waist circumference, fat mass index (fat mass in kg/m2) and lean mass index (lean mass in kg/m2).MethodsWe used data from the Tromsø Study Fit Futures, which invited all first year students in upper secondary high school in two municipalities in northern Norway in 2010–2011. They were reexamined in 2012–2013. Longitudinal data was available for 292 boys and 354 girls. We used multiple linear regression analyses to assess whether self-reported level of physical activity in leisure time at baseline predicted changes in body composition, and analysis of covariance to assess the effects of change in level of activity during follow-up on change in body composition. All analyses were performed sex-specific, and a p-value of < 0.05 was considered statistically significant.ResultsThere were no associations between self-reported leisure time physical activity in the first year of upper secondary high school and changes in any of the considered measure of body composition after 2 years of follow up, with the exception of waist circumference in boys (p = 0.05). In boys, change in fat mass index differed significantly between groups of activity change (p < 0.01), with boys adopting activity or remaining physically active having less increase in fat mass index than the consistently inactive. In girls, change in lean mass index differed significantly between groups of activity change (p = 0.04), with girls adopting physical activity having the highest increase.ConclusionsSelf-reported leisure time physical activity does not predict changes in body composition in adolescents after 2 years of follow up. Change in the level of physical activity is associated with change in fat mass index in boys and lean mass index in girls.
Highlights
It is not clear how physical activity affects body composition in adolescents
We explored the effect of adjusting for Pubertal Development Scale (PDS) or age at menarche in complete case analyses, but as this had no substantial impact on results, we did not include the variables in the final model
We found weak relationships between the frequency of leisure time physical activity at baseline and change in body composition, suggesting that change in body composition in this age group was mainly independent of level of self-reported physical activity
Summary
It is not clear how physical activity affects body composition in adolescents. Physical activity levels are often reduced during this period, and the relative proportion of body fat mass and lean mass undergo natural changes in growing adolescents. Among adolescents in the Western world there is evidence for a plateauing of the obesity epidemic at a high level [4]. Studies have shown that adolescent lifestyle tend to persist into adulthood [8, 9], emphasizing the importance of preventing overweight and obesity in this period of life. A systematic review on the relationship between body composition and physical activity in adolescents showed conflicting results, with reverse causality suggested as a possible explanation – meaning that overweight and obesity could be both a cause and an effect of low physical activity [10]. The relationship is further complicated by associations with sedentary behavior, nutrition, socioeconomic status and genetics [11,12,13,14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
