Evolving environmental factors in the obesity epidemic

This chapter presents a systematic review of available data on environmental factors that may have contributed to recent trends in population body weight. It focuses especially on the US population, for which data on environmental change and body weight are most complete. The cause of the obesity epidemic that has affected the world for the last thirty years remains unknown. Although changes in body weight and fatness are surely the result of changes in energy intake and energy expenditure that are mediated by changes in food and activity choices, there are no clear data identifying the specific contribution of energy intake versus energy expenditure, or the specific contributions of specific behavioural choices. It is argued that consideration of biological and behavioural aspects of energy intake and use strongly favour change in energy intake as the most likely cause. However, the fact that population data on energy intake and energy expenditure cannot elucidate this issue is a cause for concern.