Obesity Threatens to Cut U.S. Life Expectancy, New Analysis Suggests
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 team of scientists
supported in part by the National Institute on Aging (NIA), a component
of the National Institutes of Health (NIH) of the Department of
Health and Human Services (DHHS).
The U.S. could be facing its first sustained drop in life expectancy
in the modern era, the researchers say, but this decline is not
inevitable if Americans particularly younger ones trim their
waistlines or if other improvements outweigh the impact of obesity.
The new report in the March 17, 2005 issue of The New England
Journal of Medicine appears little more than a year after the DHHS unveiled
a new national education campaign and research strategy to combat
obesity and excessive weight.
The new analysis, by S. Jay Olshansky, PhD, of the University
of Illinois at Chicago, Leonard Hayflick, Ph.D., of the University
of California, San Francisco, Robert N. Butler, M.D., 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 reevaluation
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 Olshansky group bases 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 life styles of baby boomers and the next generation
could have on life expectancy,” says Richard M. Suzman, Ph.D.,
Associate Director of the NIA for Behavioral and Social Research.
Indeed, Suzman notes, 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,” Suzman 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
For instance, smoking significantly reduces the life expectancy
of the average smoker, Suzman says, so obesity is just one of many
factors that will need to be accounted for, together or separately,
in projecting how Americans will age. The NIA supports several
projects on population demography that forecast life and health
expectancy, research which is critically important to policy makers
looking at the implications of an aging population.
According to the NEJM report, studies suggest that two-thirds
of American adults are overweight (having a body mass index BMI of
25 or more) or obese (having a BMI of 30 or more)**. One study cited
by the authors indicates that the prevalence of obesity in U.S.
adults has increased about 50 percent per decade since 1980. Additional
research has shown that people who are severely obese with
a BMI greater than 45 live up to 20 years less than people
who are not overweight. Some researchers have estimated that obesity
causes about 300,000 deaths in the U.S. annually. In addition,
obesity is fueling an epidemic of type 2 diabetes, which also reduces
To estimate the overall effect of obesity on life expectancy in
the U.S., Olshansky and his colleagues calculated the reduction
in death rates that would occur if everyone who is currently obese
were to achieve the difficult goal of losing enough weight to reach
an “optimal” BMI of 24. The calculation was based,
in part, on age, race, and sex-specific prevalence of obesity in
the United States from the Third National Health and Nutrition
Examination Survey. Based on these calculations, the researchers
estimated that life expectancy at birth would be higher by 0.33
to 0.93 year for white men, 0.30 to 0.81 year for white women,
0.30 to 1.08 year for black men, and 0.21 to 0.73 year for black
women if obesity did not exist.
The overall reduction in life expectancy of one-third to three-fourths
of a year attributed to obesity in this analysis exceeds the negative
effect of all accidental deaths combined, and could deteriorate
over time, the researchers said.
“These trends suggest that the relative influence of obesity
on the life expectancy of future generations could be markedly
worse than it is for current generations,” Olshansky and
the authors conclude in their report. “In other words, the
life-shortening effect of obesity could rise …to two to five years, or more, in the
coming decades, as the obese who are now at younger ages carry
their elevated risk of death into middle and older ages.”
The projected decline contrasts with estimates by other leading
researchers, which predict a continuation of the historic trend
of increasing life expectancy in America and Europe dating back
to the 1850s, according to Dr. Suzman. In fact, he points out that
the experience of other developed nations is instructive as a barometer
of how much room might exist to increase U.S. life expectancy.
More than 20 other developed nations, including France, Japan,
Germany, Sweden, and the United Kingdom have a higher average life
expectancy than the U.S. Women in Japan, for example, live about
5 years longer than women in the U.S. There is little evidence
that life expectancy in these countries is approaching any kind
of limit, Suzman says.
In March 2004, the DHHS launched public awareness campaign, entitled
Healthy Lifestyles and Disease Prevention, to encourage
American families to take small, manageable steps within their
such as using the stairs instead of the elevator, to ensure effective,
long-term weight control. The campaign includes multi-media public
service announcements (PSAs) and a new interactive website, www.smallstep.gov.
In addition, the NIA has developed a free exercise guide for older
adults, which is available online at www.nia.nih.gov. The NIH
and other Federal agencies also offer free information about excessive
weight and what can be done about it, including the National Institute
of Diabetes and Digestive and Kidney Diseases http://win.niddk.nih.gov/publications/choosing.htm,
the Food and Drug Administration http://www.cfsan.fda.gov/~dms/wh-wght.html,
and the Federal Consumer Information Center http://www.pueblo.gsa.gov/cic_text/health/works4you/weightloss.htm.
This research was also supported by the Institute of Government
and Public Affairs at the University of Illinois at Chicago and
the Charles H. Hood Foundation.
The NIA is one of 27 Institutes and Centers at the National
Institutes of Health (NIH), part of the U.S. Department of Health & Human
Services. The NIA leads the Federal Government effort conducting
and supporting research on the biomedical and social and behavioral
aspects of aging and the problems of older people. For more information
on aging-related research and the NIA, please visit the NIA website
at www.nia.nih.gov. The public may also call for publications describing
these efforts and offering health information for older people
and their families at 1-800-222-2225, the toll free number for
the National Institute on Aging Information Center.
* Olshansky SJ, Passaro DJ, Hershow RC, Layden J, Carnes BA, Brody
J, Hayflick L, Butler RN, Allison DB, and Ludwig DS, “A Potential
Decline in Life Expectancy in the United States in the 21st Century,” New
England Journal of Medicine, 352:11, pp. 1138-1145.
** BMI is a number that shows body weight adjusted for height.
BMI can be calculated with simple math using inches and pounds,
or meters and kilograms. For adults aged 20 years or older, BMI
falls into one of these categories: underweight, normal, overweight,
or obese. Based on BMI, a 6-foot-tall man, for instance, is considered
overweight if he weighs more than 190 pounds and obese if he weighs
greater than 220 pounds. A 5-foot-4 woman is considered overweight
if she weighs more than 150 pounds and obese if her weight exceeds