We hypothesized that 16 weeks of school-based aerobic exercise positively affects children with overweight, partly by improving physical fitness and cognitive function. To test our hypothesis, we assessed the effect of long-term school-based aerobic exercise intervention on the physical fitness and cognitive function of children with overweight compared with a control group of children with normal weight. Comparing a diverse sample of inactive 6-year-old overweight and normal-weight children, children who were overweight had worse physical fitness and cognition. In addition, we further found that 16 weeks of aerobic exercise can improve the physical fitness and cognitive function of children with overweight. This result is associated with the positive effect of aerobic exercise, including improvement in physical fitness and cognitive function parameters, in normal-weight children.
The children with overweight have more health problems, including problems with their basic information (i.e., weight and BMI), physical fitness components (i.e., muscular strength and endurance, flexibility, and cardiopulmonary function), and cognitive function components (i.e., attention, simple reaction time, and working memory span), than that had by children with normal weight. Childhood overweight/obesity is a major public health issue in the 21st century, and there is growing evidence regarding the negative effects of overweight on physical fitness, short- and long-term functioning, and well-being[16–17]. The weight and BMI values of the children who were overweight was significantly different from those of children with normal weight. Childhood obesity is not only a precursor of adult obesity, but it is associated with an increased risk of chronic diseases, including type 2 diabetes and adolescent hypertension, and psychological illness[18–19]. The relationship between BMI and long-term cardiovascular risks due to childhood obesity has been established. The study by Lee CK was the first to explore the relationship between body composition and physical fitness in children with overweight, obesity, and severe obesity[20]. Our study also highlighted that muscular strength was associated with height and body weight in all the groups. Similar with the a previously cited study by Lee CK, our study demonstrated that childhood obesity can negatively affect physical fitness. In addition, this study further explored the cognitive function of children with overweight. The results demonstrated that the children with overweight compared with those with normal weight had worse cognitive function, including attention and simple reaction time. Childhood obesity is reported to be associated with changes in brain structure and impairment in cognitive function, such as total brain volume, inhibitory control working memory, and attention[21].
Based on the above findings, early evidence-based preventive strategies should be implemented in primary schools as soon as possible to decrease obesity and improve physical fitness. At present, the risks of childhood overweight/obesity can be decreased by dietary habits, pertinent public health initiatives, and education on sedentary lifestyles[22–23]. In addition, aerobic exercise, which almost has no side effects, can be an ideal intervention for children with overweight. Aerobic exercise has a wide range of physiological, psychological, and neurocognitive benefits under normal or disease states, including but not limited to overweight/obesity[24–25]. Aerobic exercise attenuates the effect of overweight/obesity on body morphology, such as weight and BMI[26–27]. We also demonstrated in this study that 16 weeks of school-based aerobic exercise decreases the weight and BMI of children with overweight. Rodent studies have shown that exercise can alter the physiology of adipose tissue, which enhances the mobilization of fat[28]. Increase in BMI can lead to secular declines in physical fitness[29]. In this study, we observed a significant decline in the physical fitness parameters of children with overweight, including their muscular strength, muscular endurance, flexibility, and cardiopulmonary fitness. A meta-analysis of randomized controlled trials revealed that aerobic exercise reduces the cardiovascular risk associated with children and adolescent obesity[30]. Wang et al. further revealed that exercise has positive effects on the physical, cardiorespiratory, musculoskeletal, and motor fitness of preschool children[31]. In addition, we found that aerobic exercise remarkably promoted cognitive function, including attention, simple reaction time, and working memory span in children with overweight. A systematic review by Keawtep et al. showed that in individuals who are obese, physical exercise may be an effective non-pharmacological approach to maintaining or enhancing cognitive function[32]. This systematic review findings explain why aerobic exercise has a positive effect on cognitive function in children with overweight. Such evidence collectively supports the use of aerobic exercise interventions for promoting physical fitness and cognition in children with overweight.
This study has some limitations. The sample in this study included only 6-year-old students; therefore, further studies with a larger and varied sample is still necessary to verify our study results. Furthermore, the effect of exercise on overweight in children is influenced by the form and intensity of exercise, which was not assessed in this study. Therefore, more evidence is needed to demonstrate the effect of different exercise forms and intensities in children with overweight.