The Chronicle

Issue date: 11/8/07 Section: Columns
Last update: 11/8/07 at 7:19 AM EST

Obesity is an important focus of global health efforts today because it is a premorbid state that can be preventable with increases in our scientific understanding of the sources of its "spread."

How prevalent are overweight and obesity? What is the history of changes in their manifestation? In the United States today, 66 percent of all adults are overweight or obese, with 34 percent being obese. By the year 2012, it is widely estimated that more than 70 percent of all U.S. adults will be overweight or obese, with more than 40 percent being obese.

These are staggering statistics-particularly so when one considers that since the 1970s these percentages have more than doubled.

And this apparent epidemic is evident for children as well as adults. In the United States the prevalence of children prone to obesity has increased from about 5 percent in the 1970s to more than 17 percent today. These rapid changes in American obesity prevalence are not unique-almost all of the nations of Western Europe have witnessed two- to threefold increases in obesity prevalence in both adults and children during the past three decades.

Beyond the developed nations of Western Europe and North America, there has been a sharp increase in obesity among children and adults in China, India and the Third World nations of Africa. In some of these nations, malnutrition and obesity seem to go hand-in-hand-sometimes occurring within the same household. In China, the threefold increase in childhood obesity over the past two decades is largely concentrated in urban areas, particularly Beijing. Obviously, there are unique aspects of the manifestation of the spread of obesity that are pertinent to different nations and regions of the world.

In a technical sense, obesity is not a communicable disease. In simple terms, it is a regulatory anomaly brought about by consuming more energy in food than one expends in activity. There is no apparent biological medium of transmission from person to person, nor is it an illness defined by lesions or insults to our biological systems.

So why refer to the alarming and sharp upswing in its worldwide prevalence as an epidemic or pandemic? These terms are typically reserved for communicable scourges such as bubonic plague, tuberculosis or AIDS-to cite a few painful examples from various eras in history.

In contrast, obesity seems on the surface to be the result of individual behavioral processes that create an imbalance of energy consumption and expenditure and the biogenetic and social phenomena that usher in that behaviorally determined imbalance. There are no "germs" or microbes that humans transmit to each other that make us obese.

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