Role of physical activity, sedentary behavior and physical fitness in mental health and white matter in children and adolescents

Abstract

Childhood and adolescence are periods of dynamic behavioral, cognitive and emotional development that can increase vulnerability to mental disorders. Obesity and related issues represent important public health concerns in terms of prevalence, incidence and economic burden. In addition, nearly 75% of young people have insufficient levels of physical activity in developed countries. In tandem with this fact, most of the young people are “digital natives”, which means that they have grown up surrounded by digital information and entertainment on screens. All these facts together prove that a major change in the lifestyle of young people is taking place in the last decades, which in turn might have an effect on their mental and brain health. In this context, white matter, which is important for efficient transmission of information between brain areas, has been considered one of the brain features susceptible of being modified by physical activity and other related factors (i.e., sedentary behavior and physical fitness) in young people, yet the body of evidence is still in its infancy, and further studies are needed to shed light on the many questions that remain unanswered. Therefore, the overall aim of the present International Doctoral Thesis is to study the role of physical activity, sedentary behavior and physical fitness in the mental health (part I), and white matter (part II) in young people. The general results of this Doctoral Thesis show that physical activity had a small but positive effect on mental health in young people. In terms of white matter, we did not find any significant effect on white matter microstructure after a 20-week physical exercise intervention in children with overweight or obesity, although cross-sectional studies of this Doctoral Thesis indicated a positive relationship between physical activity and white matter. Sedentary behavior seems to be negatively associated with mental health. However, the relationship with white matter microstructure is not clear yet. For instance, while we found that watching TV was negatively associated with white matter microstructure in children with overweight or obesity, no association was found in a bigger cohort of children. Future work should continue to explore longitudinal data in order to more concretely decipher the temporality of these associations. Regarding to physical fitness, muscular fitness was the most promising physical fitness component in relation to mental health, and white matter in children with overweight or obesity. Specifically, we encourage researchers to study the potential role of muscular fitness in the white matter of young people as well as the mechanisms that might be explaining this relationship. Collectively, the results of the present International Doctoral Thesis enhance our understanding about the implications that health-related behaviors and factors such as physical activity, sedentary behavior and physical fitness may have for mental and brain health in young people.