Contrary to earlier findings, excess body
fat in elderly decreases life expectancy
Elderly individuals should maintain a normal
weight, suggests Loma Linda University
research
August 15, 2011 – While some past studies
have shown that persons carrying a few extra
pounds in their 70s live longer than their
thinner counterparts, a new study that
measured subjects' weight at multiple points
over a longer period of time reveals the
opposite.
Research from Adventist Health Studies
recently published in the Journal of the
American Geriatrics Society showed that
men over 75 with a body mass index (BMI)
greater than 22.3 had a 3.7-year shorter
life expectancy, and women over 75 with a
BMI greater than 27.4 had a 2.1-year shorter
life expectancy. Generally, a BMI between
18.5 and 24.9 is considered normal weight,
and a BMI of 25 to 29.9 is considered
overweight. A BMI of 30 or more is
considered obese.
Previous work in this area by others found a
protective association for a high body
weight among the elderly. Pramil N. Singh,
DrPH, lead author of the paper and an
associate professor in the School of Public
Health at Loma Linda University, says the
data from many past studies is problematic
because only a single baseline measure of
weight was taken, which does not account for
weight changes or how weight changes affect
life expectancy. Additionally, most past
studies had mortality surveillance of fewer
than 19 years, which analyses have shown to
be an inadequate amount of time to study
risks associated with weight.
"We had a unique opportunity to do 29 years
of follow-up with a cohort that was also
followed for mortality outcomes," Dr. Singh
said. "Across this long period of time, we
had multiple measures of body weight, which
provided a more accurate assessment."
The study looked at 6,030 adults who never
smoked and who were free of major chronic
diseases at enrollment. It then examined
only those adults who maintained a stable
weight. This was done in an effort to
exclude individuals who, for example, were
in the normal weight category because they
experienced significant weight loss due to a
disease. Therefore their death would not
have been related to their normal weight,
but rather to the disease that caused them
to reach normal weight.
"When you control for confounding by
disease-related weight loss, overweight and
obesity remain a risk for persons over the
age of 75," Dr. Singh said. "This suggests
that elderly individuals of normal weight
should continue to maintain their weight."
Researchers noted a difference between
genders in that men had a higher sensitivity
to body fat than women. Men started to
experience a greater risk of mortality at a
BMI of 22.3, while this risk did not appear
for women until a BMI of 27.4. One possible
reason for the difference between genders,
Dr. Singh said, is that body fat is the
primary source of estrogen in
post-menopausal females, and a minimum level
of estrogen in those years can be protective
against heart disease and hip fractures.
"This is not to say that extra weight is
good for women over 75," Dr. Singh said,
"but rather that the negative effects of
extra weight in women over 75 appear at a
higher weight than in males."
The study population itself is unique in
that all were Seventh-day Adventists, who,
because of church recommendations, are
lifelong non-smokers, consume little if any
alcohol, are more physically active, and
consume less meat than the general
population. This means those who maintained
a lower BMI did so intentionally with
healthy lifestyle choices rather than as a
result of smoking for weight control or as a
result of poverty-related factors. Dr. Singh
said further studies are needed to
understand the positive and negative effects
of lifestyle patterns that help individuals
maintain low body weight over long periods
of time.
