The prevalence of obesity in preschool children has increased dramatically in the last 30 years. At the same time, children’s physical activity levels have decreased and sedentary behaviours have increased. These trends are of great concern for public health due to their immediate and long-term consequences for the health of affected individuals. The preschool years (age 3-5 years) are regarded as critical for the establishment of a healthy lifestyle and a healthy weight. Yet, little is known about this young population. The thesis at hand provided a better understanding of the relationship of physical activity and sedentary behaviour with adiposity and the influence of the childcare environment on these factors in preschool children.
This research is based on the Swiss Preschoolers’ Health Study (SPLASHY), a multi- site prospective cohort study aimed at understanding the influence of stress and physical activity on preschool children’s psychological and physiological health. This thesis assessed and analysed cross-sectional and longitudinal measures of physical activity, sedentary behaviour and adiposity. Furthermore, it evaluated the influence of the child-care environment on physical activity, sedentary behaviour and adiposity.
Cross-sectional results identified a number of relevant factors: more frequent child- initiated interactions with other children during childcare, mixing different ages within a childcare group, the presence of a written physical activity convention, and/or a larger childcare surface. These were related to children’s physical activity and sedentary behaviour during childcare days and mostly also to overall physical activity on both home and childcare days. Parental involvement in childcare physical activity projects correlated with reduced body fat. In addition, cross-sectional analyses showed that physical activity was positively associated with BMI and waist circumference in both the total population and in the normal weight group. Vigorous physical activity was negatively associated with body fat in the overweight and obese group, but not in the normal weight group. Longitudinal results showed that higher levels of total physical activity and moderate-to-vigorous physical activity predicted lower adiposity 1 year later. Sedentary behaviour did not predict adiposity 1 year later. Furthermore, adiposity did not predict physical activity nor sedentary behaviour.
These findings contribute to the current understanding of the relationship of physical activity behaviours with adiposity and confirm the benefits of being active from early childhood. We have identified particular childcare correlates of physical activity, sedentary behaviour, and adiposity that can be valuable targets for change in future interventions. Furthermore, encouraging children to engage in physical activity of at least moderate intensity may be more important to public health than reducing sedentary behaviour for preventing obesity in healthy preschool children.