The role of physical activity in the prevention of obesity

Obesity rates are increasing around the world.  Obesity develops as a consequence of positive energy balance where energy intake, over some period of time, exceeds energy intake. While some experts argue about the relative importance of energy intake vs. energy expenditure, I believe that obesity can only be understood by considering both energy intake and expenditure. Understanding the role of physical activity in body weight regulation requires an understanding of how the body achieves energy balance. Physical activity can potentially contribute to maintenance of healthy body weight in two ways. First, the more physical activity the more calories burned and the more calories that can be consumed without weight gain. Second, the body appears to be biased toward achieving energy balance at a high vs. low energy flux (total daily energy flow through the body). At a high energy flux, energy intake is more closely linked to energy expenditure, thus providing a physiological advantage for maintaining a healthy body weight. A high energy flux can be achieved through a high level of physical activity or through a high body mass. Empirical data suggests that high levels of physical activity are protective against weight gain and that high levels of physical activity are critical in preventing weight gain after weight loss. Appreciating the interaction between energy intake and energy expenditure can be important for developing strategies to reduce global rates of obesity