Obesity Threatens U.S. Life Expectancy

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Over the next few decades, life expectancy for the average American could decline by as much as 5 years unless aggressive efforts are made to slow rising rates of obesity, according to a report in The New England Journal of Medicine. The report warns that the U.S. could be facing its first sustained drop in life expectancy in the modern era, but this decline is not inevitable if Americans—particularly young people—trim their waistlines or if other improvements outweigh the impact of obesity.

The report appears little more than a year after the Department of Health and Human Services unveiled a new national education campaign and research strategy to combat obesity and excessive weight. The new analysis, by Dr. S. Jay Olshansky, professor of epidemiology at the University of Illinois at Chicago, Dr. Leonard Hayflick, professor of anatomy at the University of California, San Francisco, Dr. Robert N. Butler of the International Longevity Center in New York, and others suggests that the methods used to establish life expectancy projections, which have long been based on historic trends, need to be reassessed. This re-evaluation is particularly important, they say, as obesity rates surge in today’s children and young adults. “Forecasting life expectancy by extrapolating from the past is like forecasting the weather on the basis of its history,” Olshansky and his colleagues write. “Looking out the window, we see a threatening storm—obesity—that will, if unchecked, have a negative effect on life expectancy.”

Unlike historic life expectancy forecasts, which rely on past mortality trends, the study group based their projection on an analysis of body mass indexes and other factors that could potentially affect the health and well-being of the current generation of children and young adults, some of whom began having weight problems very early in life. The authors say that unless steps are taken to curb excessive weight gain, younger Americans will likely face a greater risk of mortality throughout life than previous generations.

“This work paints a disturbing portrait of the potential effect that lifestyles of baby boomers and the next generation could have on life expectancy,” says Dr. Howard M. Suzman, associate director of the National Institute on Aging, which provided support for the study. Suzman notes that obesity may already have had an effect. The sharp increase of obesity among people now in their 60s, he suggests, may be one explanation why the gains in U.S. life expectancy at older ages have been less than those of other developed countries in recent years.

“But it is critical to note that the reduced life expectancy forecast by the study is not inevitable, and there is room for optimism,” he says. “Government and private sector efforts are mobilizing against obesity, and increased education, improved medical treatments, and reduced smoking can tip the balance in favor of reduced mortality and continued improvements in life expectancy.”

This view is echoed in an editorial that accompanies the NEJM report. “The fact that the U.S. population has already shown the ability to shift to healthier lifestyles is encouraging,” writes Dr. Samuel H. Preston, Fredrick J. Warren professor of demography at the University of Pennsylvania. He points out that 42% of U.S. adults were smokers in 1965, as compared with 23% in 2001, and that the percentage of Americans 20 to 74 years of age with high levels of serum cholesterol fell from 33% in 1961 to 18% in 1999 and 2000. “Primarily because of behavioral changes, the incidence of AIDS has fallen by nearly 50% since 1992,” he adds. “The fact that most health-related behaviors have improved while obesity has worsened may be an indication of just how daunting the prospect of reducing levels of obesity may be. The rising prevalence and severity of obesity are already reducing life expectancy among the U.S. population. A failure to address the problem could impede the improvements in longevity that are otherwise in store.”

For more details, see The New England Journal of Medicine, March 17, 2005, vol 352, 1138–1145; 1135–1137.