Bélanger, M., O’Loughlin, J., Karp, I., A Barnett, T. et Sabiston, C. (2012). Physical activity fluctuations and body fat during adolescence. Pediatric obesity, 7, 73-81.
Objective : The objective of the study was to test the hypothesis that greater fluctuations in physical activity lead to greater increases in body fat during adolescence.
Methods : Seven hundred fifty‐six adolescents in Montreal, Canada, aged 12–13 years at baseline, completed a 7‐d physical activity recall questionnaire every 3 months over 5 years. Body mass index (BMI), waist circumference, and triceps and subscapular skinfold thickness were measured at baseline and at the end of follow‐up. Subject‐specific linear regressions, expressing physical activity as a function of time, were fitted and physical activity fluctuation scores were obtained by averaging the absolute values of regression residuals. The association between body fat after 5 years and the physical activity fluctuation score was assessed in linear regressions adjusting for baseline body fat, average number of physical activity sessions per week, diet and sociodemographic variables.
Results : Among boys, there were statistically significant positive associations between physical activity fluctuation and BMI (β, 95% confidence interval: 0.12, 0.02–0.21) and triceps skinfold (0.40, 0.17–0.63). The associations with waist circumference or subscapular skinfold were not statistically significant (0.22, −0.04–0.49; 0.13, −0.05–0.32, respectively). In girls, there were statistically significant negative associations between physical activity fluctuation and BMI (−0.12, −0.20 to −0.03), waist circumference (−0.54, −0.91 to −0.17), subscapular skinfold (−0.41, −0.56 to −0.26) and triceps skinfold (−0.22, −0.38 to −0.05).
Conclusion : Physical activity fluctuations appear to affect body fat during adolescence. Sex‐specific interventions may be needed given that greater physical activity fluctuations seem unfavourable for boys and beneficial for girls.