An explosive rise in obesity may cause life expectancy in the U.S. to level off or decline by 2050, according to a new study.
In the 20th century, U.S. life expectancy climbed from 47 to its present height of mid to late 70's, a rise unprecedented in human history. The fastest part of the increase occurred in the first few decades of the century, as improved sanitation and nutrition dramatically reduced infant and child mortality.
If the new study is correct, the unprecedented rise in life expectancy will be followed by an equally unprecedented fall. A 10-person research team led by S. Jay Olshansky of the University of Illinois, Chicago, and David S. Ludwig of Children's Hospital in Boston, Massachusetts, examined data from Centers for Disease Control's big National Health and Nutrition Examination Surveys. "We tried to answer a simple question," says Olshanksy. "What would life expectancy be like in the U.S. if obesity did not exist?"
The researchers found that increasing levels of obesity, especially childhood obesity, has already offset increasing life expectancy "by 0.33 to 0.93 year for white males," with similar offsets for women and other races. Assuming that current trends continue and that no big technical fixes emerge, Olshansky says, "we have strong reason to believe this number will rise rapidly in the coming decades."
Although Olshansky stresses that the estimate is "a first-pass approximation," he believes the effect is large enough to demonstrate "that trends in obesity in younger ages will lead to significantly higher rates of mortality in the future--we will lose 2 to 5 or more years [of life expectancy] in the coming decades" if the obesity epidemic continues unchecked. If the projections—published today in the New England Journal of Medicine--come true, he notes, the next generations will be the first in recorded history to die younger and sicker than their parents--a public-health catastrophe.
That conclusion is likely to be controversial. Critics argue that it is based on a partial reading of the evidence. "Obesity is indeed a problem," says James Vaupel, director of the Max Planck Institute for Demographic Research in Rostock, Germany. "But on the other side there are extraordinary advances being made as a result of biomedical research." Moreover, he says, "the United States has seen a slowdown in life expectancy, but in other countries it's going up fairly rapidly—about 3 months per year in places like France and Japan."
National Health and Nutrition Examination Survey