Study finds life expectancy for young adults diminished by obesity

NEW YORK Though the number of Americans who smoke has decreased dramatically in recent years, increases in obesity threaten to erase potential gains in the average life expectancy of young adults, according to a new study.

A team of researchers, led by Susan Stewart of the nonprofit National Bureau of Economic Research, published the study Thursday in The New England Journal of Medicine, forecasting the life expectancy of the average 18-year-old between 2005 and 2020 by comparing data on smoking and obesity.

The researchers used National Health Interview Survey data on smoking from two-year intervals between 1978 and 2006, as well as past trends in body-mass index based on data from the National Health and Nutrition Examination Survey in four- to six-year intervals between 1971 and 2006. They also factored in the 2003 Medical Expenditure Panel Survey to examine the effects of smoking and body-mass index on health-related quality of life.

While declining rates of smoking would increase the average life expectancy of 18-year-olds, increasing rates of obesity would push it back down by eight to 11 months, the researchers found. By contrast, if all adults in the United States became nonsmokers of normal weight, life expectancies would increase by up to five years.

“If past obesity trends continue unchecked, the negative effects on the health of the U.S. population will increasingly outweigh the positive effects gained from declining smoking rates,” the authors wrote. “Failure to address continued increases in obesity could result in an erosion of the pattern of steady gains in health observed since early in the 20th century.”