Americans are facing the first sustained drop in life
expectancy in modern history because of the rapid rise
in obesity, according to a provocative new analysis.
Average life spans in the United States, which have been
steadily increasing over the past century, could be
shortened by two to five years in coming decades unless
aggressive efforts are taken to slow the obesity
epidemic, a diverse group of 10 scientists contends in
an article published in the New England Journal of
Medicine.
The authors of the new analysis are respected scientists
in a variety of fields, including Leonard Hayflick, a
cell biologist and longevity specialist at UCSF, and Dr.
Robert Butler, a former director of the National
Institute on Aging.
"The youth of today may, on average, live less healthy
and possibly even shorter lives than their parents,"
writes the group of scientists, led by University of
Illinois demographer S. Jay Olshansky.
Already, they calculate, illnesses caused by obesity
have reduced life expectancy in the United States by
four to nine months. That is more than the combined
effect of car crashes, homicides and suicides, and it
approaches the effects of heart disease and cancer on
life expectancy.
Currently, the life expectancy for someone born in the
United States is 77.6 years. Except for disease
outbreaks and wars, that statistic has been steadily
rising since the mid-1800s.
The new report - part scientific analysis, part call to
action - says that the easy gains in longevity, such as
curing childhood illness, have been made. Current
methods for calculating life expectancy, it argues, need
to be reassessed in light of the oncoming obesity
epidemic.
"Forecasting life expectancy by extrapolating from the
past is like forecasting the weather on the basis of its
history," the scientists write. "Looking out the window,
we see a threatening storm - obesity - that will, if
unchecked, have a negative effect on life expectancy."
Estimates of U.S. life spans, they noted, have important
implications for government policy. Federal tax rates as
well as benefits from social-entitlement programs, such
as Social Security and Medicare, are all based in part
on life expectancy projections for the nation's
population.
Today, two-thirds of U.S. adults are overweight,
including one-third who are obese, as measured by the
body mass index, a standard measurement of height and
weight. Current trends indicate that the prevalence of
obesity will continue to rise and affect ever younger
age groups.
Minority groups have seen especially sharp increases in
childhood and adult obesity.
Obesity significantly increases the risk of death from a
variety of health problems, including diabetes, cancer
and heart disease. Among the severely obese, life
expectancy is reduced by an estimated five to 20 years,
according to one study.
Using data from a large federal assessment of obesity
rates, the researchers calculated how much longer life
expectancy would be if everyone who is currently obese
were to lose enough weight to obtain an optimal body
mass index of 24.
If obesity did not exist, the authors "conservatively
estimated" that life expectancy would be four to 11
months longer for white men, four to 10 months longer
for white women, four to 13 months longer for black men
and three to nine months longer for black women.
The authors said the estimate was conservative in part
because it focused only on adults. As obese children
age, "the life-shortening effect of obesity could rise
from its current level of about one-third to
three-fourths of a year to two to five years, or more,
in the coming decades," they wrote.
Richard Suzman, associate director of the National
Institute on Aging, which provided funding for the
study, said the analysis broke new ground. "This work
paints a disturbing portrait of the potential effect
that lifestyles of Baby Boomers and the next generation
could have on life expectancy," he said.
The sharp increase in obesity among Americans in their
60s may help explain why the gains in U.S. life
expectancy at older ages have been less than those of
other developed nations, Suzman said. More than 20
countries, including France, Japan, Germany, Sweden and
Britain, have a higher life expectancy. Women in Japan,
for example, live about five years longer than women in
the United States.
But Suzman and others said the reduction in life
expectancy was not inevitable.
"There is room for optimism," he said. "The National
Institutes of Health and other parts of the Public
Health Service have recognized that this is a serious
health problem and begun to take action. It's
theoretically reversible."
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References:
worldhealth.net
The
New England Journal of Medicine
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