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Study: Overweight People Live Longer
But extreme underweight, obesity linked to earlier
death
By Salynn Boyles
WebMD Health News
June
25, 2009 -- There is more evidence that people who
are overweight tend to live longer than people who
are underweight, normal weight, or obese.
In a
newly published study, people who were underweight
and those who were extremely obese died the
earliest.
People who were overweight, but not obese, actually
lived longer than people whose weight was considered
normal, based on body mass index (BMI).
The
research is not the first to suggest that those who
carry a little, but not too much, extra weight tend
to survive longer than people who don't.
CDC
researchers found the same thing in a widely
reported study published in 2005, and last month a
separate group of investigators reported that
overweight heart patients live longer than lean
ones.
The Obesity Paradox
It
is becoming known as the "obesity paradox," but this
is something of a misnomer. That's because few
studies have linked obesity with longer life.
Rather, the studies generally suggest that people
with a BMI of 25 to 29.9 -- which is considered
overweight but not obese -- have a survival
advantage over people with higher or lower BMIs.
BMI,
which is a measure of body fat based on a person's
height and weight, is used to classify people into
weight categories -- underweight, normal weight,
overweight, and obese.
Based on BMI scores, a 5-foot, 5-inch adult would be
considered:
-
Underweight at 110 pounds or less (BMI <18.5)
-
Normal weight at 111 to 149 pounds (BMI =
18.5-24.9)
-
Overweight at 150 to 179 pounds (BMI = 25-29.9)
-
Obese at 180 to 210 pounds (BMI = 30-34.9)
-
Extremely obese at 211 pounds or more (BMI = 35
or greater)
In
the newly published study, researchers used data
from an ongoing Canadian national health survey to
follow more than 11,000 adults from the mid-1990s to
2007.
Compared to people who fell into the normal-weight
category:
-
Those classified as underweight were 73% more
likely to die.
-
Those classified as extremely obese with BMI of
35 or greater were 36% more likely to die.
-
Those classified as obese with BMI 30-34.9 had
about the same risk of death.
-
Those classified as overweight with BMI 25-29.9
were 17% less likely to die.
The
study appears online this week in the journal
Obesity.
It
was conducted by researchers with Statistics Canada,
McGill University, and the Kaiser Permanente Center
for Health Research and funded by grants from the
National Institute on Aging, the National Institute
of Diabetes and Digestive and Kidney Diseases, and
the Canadian Embassy.
Kaiser's David Feeny, PhD, who was a co-author of
the study, tells WebMD that there are theories, but
no hard evidence, to explain why carrying a few
extra pounds may add a few years to your life.
Overweight People Get More Treatment
Being extremely underweight is considered a marker
for poor health and frailty in older adults. Even
though the researchers tried to control for this,
poor health could explain why study participants who
weighed the least had the biggest risk of dying.
But
it is less clear why those who are overweight would
have a lower risk of death than those whose weight
is considered normal.
Because being overweight is a risk factor for a host
of chronic diseases, including heart disease and
diabetes, one theory is that their survival
advantage is due to the fact that they receive more
aggressive treatments to prevent these conditions.
"We
tend to be quicker to prescribe statins (to lower
cholesterol) and drugs to control blood pressure to
patients who are overweight and we are more likely
to screen them for diabetes," says weight management
expert Keith Bachman, MD.
Bachman leads Kaiser's Weight Management Initiative,
but he was not involved with the study.
Because the study only examined death risk, and not
disease incidence or quality of life, the risk vs.
benefit profile of carrying a few extra pounds is
unclear, Bachman says.
"Good health is more than a BMI or a number on a
scale," he says. "We know that people who choose a
healthy lifestyle enjoy better health."
Feeny adds that lifestyle choices such as eating
well, exercising regularly, managing stress, and
treating risk factors for chronic disease may be
more important for longevity than losing a few extra
pounds.
"And
this certainly doesn't mean that people who are
normal weight should go out and binge on ice cream
to gain a few pounds," he says. "The dairy industry
might like that, but it would not be a good idea."
©
WebMD. All rights reserved.
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"Good health is more than a BMI
or a number on a scale," we know that people who
choose a healthy lifestyle enjoy better health." |
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