Physical activity in relation to overweight and obesity in children and adolescents

Fitness and physical activity levels of children and adolescents are commonly addressed but data on scientific investigations are both equivocal and methodologically diverse. The intensity and type of physical activity that benefit health and development during childhood are not known. Measurement of activity in children is problematic since there is no valid method of assessing activity levels that is feasible for use in large field studies. Most studies using self-report methods, heart rate studies using low heart rate threshold and doubly labelled water studies indicate relatively high levels of activity in children. The three national surveys on large representative samples reported that 60% to 70% of all children were involved in sufficient physical activity according to various definitions. Heart rate studies demonstrate that children generally perform short bouts of moderate to vigorous activities and seldom participate in long-sustained vigorous activities. They also proved that children perform large volumes of activity in the lower heart rate zones. It is generally accepted that boys are more active than girls and physical activity declines by age (peak around 13 to 14 years of age). The difference between the physical activity of European and North American children or between children living in different European countries is difficult to judge due to the diversity of methodology and definitions.

There is a need to identify more clearly the quantity and type of activity which improves the health and promotes the normal development of children and to improve the methods assessing physical activity.