The role of nutrition and physical activity in the obesity epidemic

This chapter reviews information on temporal trends in energy intake and energy expenditure in the USA and discusses the quality and limitations of available data. The focus is on trends in the USA, firstly because surveillance data is available for the USA, and secondly because of the complications of differences in obesity trends across countries. The surveillance issues that have arisen in the USA serve as a valuable example for other countries regarding the pitfalls of tracking risk factors for obesity. Further, because the USA has experienced a steady and steep increase in the prevalence of obesity over the past twenty-five years, it serves as good case study for attempts to understand the relative contributions of diet and physical activity to the development of obesity.