Highlights From the North American Society for the Study of Obesity Annual Meeting: A Physician's View

Raymond A. Plodkowski, MD


December 01, 2003

In This Article

Energy Imbalance as a Cause of Obesity

To understand the obesity epidemic, 2 trends must be considered: increasing energy intake and decreasing energy expenditure. In the United States, there is an abundance of calorie-rich foods available to the majority of the population. In addition, the demands of everyday life have decreased the time available for food preparation. This has led to increased consumption of "fast-food" and processed foods that are often calorie dense.[4] In the past, caloric intake often was offset by physical activity. However, with industrialization, society has become increasingly sedentary. The evolution of computers and the Internet has led to a more sedentary workplace. At home, television, remote controls, and videogames have replaced outdoor physical activities.[5] Conveniences such as automobiles and mass transit have decreased the energy expended in traveling.

A study presented at the NAASO meeting proposed "urban sprawl" as another possible source of physical inactivity.[6] The investigators, Opez and colleagues, calculated sprawl levels for all US metropolitan areas using a metric based on population density and concentration. The source of data on physical activity was the Behavioral Risk Factor Surveillance System (an annual nationwide telephone survey of US adults). The level of sprawl positively correlated with physical inactivity. The authors hypothesized that urban sprawl increases driving and decreases the use of non-car transportation (walking and biking). Alternatively or additionally, increased driving times might decrease the amount of time available for physical activity. Thus, when increased caloric intake is combined with decreased physical activity, excess energy is stored and steadily accumulates as adipose tissue over time.


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