<p>Various factors, including low levels of physical activity (PA), and high consumption levels of sugar-sweetened drinks (SD), have been implicated in the general increase of fat mass (FM) levels seen in youth. <b>Purpose</b>: To determine if a significant relationship exists between fat mass (FM) and physical activity (PA) or sugar-sweetened drink (SD), in boys and girls, using longitudinal analysis. <b>Methods</b>: 105 boys and 103 girls were assessed repeatedly during childhood and adolescence, for a maximum of 7 years. Height was measured annually, as was fat free mass (FFM) and FM estimated by dual X-ray absorptiometry (DXA). PA was evaluated bi-annually using a questionnaire for children (PAQ-C/A: 1 low, 5 high), and SD was assessed using a 24-hour dietary intake questionnaire completed 1-4 times/year. Years from peak height velocity were used as a biological age indicator. Random effects models were used to analyze the data, subsequent to log linearization of the FM variable since it was not initially normally distributed. <b>Results</b>: The constructed model, controlling for maturation, FFM, and adjusted energy intake, found no interaction effect between SD and PA (p>0.05). After removal of the interaction term from the model, SD was found to have no significant relationship (p>0.05) with FM of boys or girls. In contrast, PA level was found to have a significant relationship (p<0.05) with FM of males; but not with FM of females. <b>Conclusion</b>: The longitudinal models employed revealed a significant negative relationship between level of PA and FM in males but not females, after controlling for maturational status, body size and dietary energy intake. This finding lends support, to proponents of increasing PA in youth to control FM. Regarding SD and FM, the models employed showed no relationship. Future investigation with more complex models, accounting for more covariates, may be warranted in this area.</p>

<p>Various factors, including low levels of physical activity (PA), and high consumption levels of sugar-sweetened drinks (SD), have been implicated in the general increase of fat mass (FM) levels seen in youth. <b>Purpose</b>: To determine if a significant relationship exists between fat mass (FM) and physical activity (PA) or sugar-sweetened drink (SD), in boys and girls, using longitudinal analysis. <b>Methods</b>: 105 boys and 103 girls were assessed repeatedly during childhood and adolescence, for a maximum of 7 years. Height was measured annually, as was fat free mass (FFM) and FM estimated by dual X-ray absorptiometry (DXA). PA was evaluated bi-annually using a questionnaire for children (PAQ-C/A: 1 low, 5 high), and SD was assessed using a 24-hour dietary intake questionnaire completed 1-4 times/year. Years from peak height velocity were used as a biological age indicator. Random effects models were used to analyze the data, subsequent to log linearization of the FM variable since it was not initially normally distributed. <b>Results</b>: The constructed model, controlling for maturation, FFM, and adjusted energy intake, found no interaction effect between SD and PA (p>0.05). After removal of the interaction term from the model, SD was found to have no significant relationship (p>0.05) with FM of boys or girls. In contrast, PA level was found to have a significant relationship (p<0.05) with FM of males; but not with FM of females. <b>Conclusion</b>: The longitudinal models employed revealed a significant negative relationship between level of PA and FM in males but not females, after controlling for maturational status, body size and dietary energy intake. This finding lends support, to proponents of increasing PA in youth to control FM. Regarding SD and FM, the models employed showed no relationship. Future investigation with more complex models, accounting for more covariates, may be warranted in this area.</p>