Obese Children Do Not Need to Increase Their Physical Activity Any More than Their Lean Counterparts Do.

Abstract

The relationship between child physical activity (PA) levels and obesity has been studied extensively (1, 2). Studies have often shown that obese children and adolescents spend more time in sedentary behavior and less time in non-sedentary behavior, such as moderate-to-vigorous physical activity (MVPA) (3, 4). Accordingly, at least one review of cross-sectional studies examining the link between PA and obesity has found higher levels of PA associated with lower measures of adiposity (2). Some individuals may interpret these suggestions as meaning that obese children need to increase their PA levels to attain a “healthy” weight. Despite the fact that PA generally produces very modest weight loss (randomized controlled trials typically show less than 2 kg of weight loss from exercise interventions), the perception exists, among laypeople and health professionals alike, that obese individuals are lazy and need to “get off the couch” and that a lack of exercise is an important cause of child obesity (5–7). Is a lack of activity really driving the difference in body composition between normal weight and obese children? It has been suggested that although obese children may move less than normal weight children, they are likely expending just as much, if not more, energy from PA due to a higher metabolic cost of movement (they have a larger body to carry) (5). Additionally, PA levels are extremely low among normal weight and obese children alike, whereas PA remains important for overall physical and mental health (8). This suggests that PA needs to be promoted in all children regardless of weight status, and the view that obese children need to be more targeted for extra PA because of their weight is misleading. We intend to explore this suggestion further and suggest that although patterns of PA may differ between overweight/obese and normal weight children, these are not sufficient to explain differences in weight status. Alternative interpretations of the relationship between obesity and PA are also discussed.