Symposium on ‘Nutrition and health in children and adolescents’ Session 4: Obesity prevention in children and adolescents The effect of physical activity on body fatness in children and adolescents

Abstract

With the increasing prevalence of childhood obesity, there is an urgent need to identify risk factors that are amenable to preventative action. However, there is a remarkable lack of consistency between studies that have investigated the relationships between measurements of physical activity and energy expenditure and body fatness in children. This disparity could be because energy intake is a more important determinant in preventing obesity. Alternatively, some of the conflicting results could be related to methodological limitations in assessing activity and body composition. Erroneous conclusions may be drawn if physical activity energy expenditure is not adjusted for differences in body composition, or body fat is not appropriately adjusted for body size. For public health purposes it may be more informative to evaluate the amount and intensity of physical activity required to prevent fat-mass gain than to assess energy expended in physical activity. The lack of consensus in the cut-off points applied to define intensity levels is severely hindering comparisons between studies using accelerometers that have examined relationships between activity intensity and body fatness. Thus, it is not currently possible to develop a firm evidence base on which to establish physical activity recommendations until the limitations are addressed and more prospective studies undertaken. In order to turn research into effective prevention strategies a clearer understanding of the psycho-social, behavioural and environmental factors that influence activity is needed, including the interactions between physical activity and other behaviours such as time spent sedentary, sleeping and eating. Childhood obesity: Physical activity: Energy expenditure: Body fatnessThe prevalence of childhood obesity continues to rise (Lobstein et al. 2004) and there is an urgent need to identify risk factors that are amenable to intervention and preventative action. Over the medium to long term, at least, it is clear that to prevent excessive positive energy balance over and above the needs for growth, and thus excess fat-mass gain, energy intake must equal total energy expenditure (TEE). On the TEE side of the energy balance equation, physical activity is the most variable and amenable component for intervention efforts.At present there is no compelling empirical evidence on which to base physical activity recommendations in children and adolescents in order to prevent excess weight gain. From the limited information available for children, combined with extrapolation of evidence for adults, the current general consensus is that children should undertake at least 60 min of at least moderate-intensity activity each day for general health (Department of Health, 2004). There are no objective historical data on levels of physical activity from which to compare past and present activity in Abbreviations: AEE, activity energy expenditure; DLW, doubly-labelled water; FFM, fat-free mass; HR, heart rate; HRM, HR monitoring; PAL, physical activity level; TE...

Organized Physical Activity in Young School Children and Subsequent 4-Year Change in Body Mass Index

“…A number of studies, however, have shown that physical activity and energy intake have independent associations with adiposity. 35–38 A third limitation was the use of BMI as the primary indicator of obesity risk in children. The accurracy of BMI as an indicator of body fatness varies according to adiposity level.…”