%0 Journal Article %T The Relation between Aerobic Fitness, Muscular Fitness, and Obesity in Children from Three Countries at Different Stages of the Physical Activity Transition %A M. H¨¦roux %A V. Onywera %A M. S. Tremblay %A K. B. Adamo %A J. Lopez Taylor %A E. J¨¢uregui Ulloa %A I. Janssen %J ISRN Obesity %D 2013 %R 10.1155/2013/134835 %X Background. The physical activity transition is contributing to an increase in childhood obesity and a decrease in fitness worldwide. This study compared body composition and fitness measures in children from three countries and examined intercountry differences in the relationship between these variables. Methods. Participants consisted of 736 Canadian, 193 Mexican, and 179 Kenyan children aged 9¨C13 years. Body mass index (BMI), waist circumference, triceps skinfolds, aerobic fitness, and muscular fitness were measured. Linear regression was used to examine associations between variables. Results. The prevalence of obesity was the highest in Mexican children (9.2% boys, 8.4% girls) and the lowest in Kenyan children (0.9% boys, 2.8% girls). Aerobic fitness ( in mL/kg/min) was the highest in Kenyan children (50.2 boys, 46.7 girls) and the lowest in Canadian children (41.3 boys, 38.3 girls). Aerobic fitness was negatively associated with body composition measures irrespective of country and sex. Mexican children with low aerobic fitness had higher body composition measures than Canadian and Kenyan children. Muscular fitness was not associated with the body composition measures in Kenyan children but was a weak positive correlate of BMI and waist circumference in Canadian and Mexican children. Conclusion. The current study provides some evidence to support the physical activity transition hypothesis. 1. Introduction Childhood obesity has reached epidemic proportions [1]. Increases in weight and adiposity at the population level were first observed in high-income Western countries [2]. Research has linked these body composition changes to the nutrition and physical activity transitions which are characterized by an increased consumption of refined and processed foods and decreased levels of physical activity and are closely associated with social and economic changes impacting urbanization, food systems, labour demands, and transportation choices [2¨C5]. These transitions seem to be occurring simultaneously and low- and middle-income countries are now progressing through them experiencing similar body composition changes to those that have already occurred in high-income countries [6¨C8]. In fact, in the last decade the prevalence of obesity has tripled in several low- and middle-income countries [9]. As a result, obesity and its related chronic diseases are significant public health issues worldwide [10, 11]. In addition to the rise in childhood obesity and inactive lifestyles, secular changes in children¡¯s fitness¡ªa strong and independent marker of chronic %U http://www.hindawi.com/journals/isrn.obesity/2013/134835/