Laziness
Increases Dangerous Organ Fat
People who don’t
exercise build dangerous fat among their organs more quickly than
previously thought, according to a study.
Researchers looked
at visceral fat, fat among the organs that is often invisible
but is linked with insulin resistance (pre-diabetes), heart disease
and other metabolic syndromes.
The study involved
170 volunteers who were grouped according to exercise. One group
got no exercise, another got small amounts of moderate exercise
(equivalent to walking 11 miles a week), a third group got low
amounts of vigorous exercise (equivalent to jogging 11 miles a
week), and a final group got lots of vigorous exercise (equivalent
to jogging 17 miles a week).
It was found that volunteers
who did not exercise had an 8.6 percent increase in visceral fat
after eight months, while those who exercised the most lost 8.1
percent of their visceral fat during that time.
Women volunteers gained
visceral fat twice as quickly as men, according to researchers.
Researchers noted that
the rapid increase in visceral fat among sedentary overweight
adults mirrors the increasingly rapid rise in obesity in the United
States. Currently, two out of three adults are obese or overweight.
On a positive note,
exercise was found to take the fat away quickly. Volunteers who
jogged for 17 miles each week had significant decreases in visceral
fat, subcutaneous abdominal fat, which lies under the skin, and
total abdominal fat.
50th Annual American
College Of Sports Medicine May 28, 2003
Physical Inactivity
Rapidly Increases Visceral Fat; Exercise Can Reverse Accumulation
SAN FRANCISCO -- In findings that should add to the national debate
over rising obesity rates in the U.S., Duke University Medical
Center researchers have demonstrated that physical inactivity
leads to a significant increase in potentially dangerous visceral
fat, while high amounts of exercise can lead to significant decreases
in such fat over a fairly short time period.
The researchers also
found that while lower amounts of exercise prevented the significant
accumulation of visceral fat seen in the controls, it did not
lead to the improvements seen in participants with higher levels
of exercise.
Controlling visceral
fat is important, the researchers say, because increased levels
have been associated with insulin resistance, cardiovascular disease
and other metabolic syndromes. Visceral fat is located around
the organs inside the belly and is deeper in the body than subcutaneous
fat, which lies under the skin.
In the first randomized
clinical trial to evaluate the effects of varying amounts and
intensities of exercise in sedentary overweight men and women,
the researchers were surprised at how rapidly fat accumulated
deep in the abdomens of study participants who did not exercise.
This rapid accumulation of visceral fat emphasizes the high cost
of a sedentary lifestyle.
"The results of
our investigation show that in sedentary overweight adults who
continue to choose a sedentary lifestyle the detrimental effects
are worse and more rapid than we previously thought," said
Cris Slentz, Ph.D., who presented the results of the Duke study
today (May 28, 2003) during the 50th annual scientific sessions
of the American College of Sports Medicine. "We probably
should not have been surprised since this simply mirrors the increasingly
rapid rise in obesity prevalence seen in the U.S., where presently
two out of three adults are overweight or obese.
"On the other
hand, participants who exercised at a level equivalent to 17 miles
of jogging each week saw significant declines in visceral fat,
subcutaneous abdominal fat and total abdominal fat," Slentz
continued. "While this may seem like a lot of exercise our
previously sedentary and overweight subjects were quite capable
of doing this amount."
Specifically, participants
who did not exercise had an 8.6 percent increase in visceral fat
after eight months, while those participants who exercised at
the highest amount saw a 8.1 percent decrease in visceral fat.
Additionally, the Duke
team found interesting difference between men and women.
"In the group
of subjects who did not exercise, the men had a 1.5 percent increase
in weight, while the women had a 0.6 percent increase," Slentz
said. "However, the women experienced an 11.6 percent increase
in visceral fat, more than twice the amount of the men (5.7 percent).
That the women experience less of a weight gain but gained a higher
proportion of visceral fat suggests an aggressive accumulation
in women that needs further study."
To better understand
the effects of differing amounts of exercise, the researchers
randomized 170 participants into one of four groups: no exercise,
low dose/moderate intensity (equivalent of 11 miles of walking
per week), low dose/vigorous intensity (11 miles of jogging per
week) or high dose/vigorous intensity (17 miles of jogging per
week).
The exercise was carried
out on treadmills, elliptical trainers or cycle ergometers in
a supervised setting. In order to determine the role of exercise
alone, participants were not allowed to change their diet during
the course of the study. The researchers used computed tomography
(CT) both before exercise and eight months later to determine
the extent and distribution of fat change.
"There were no
significant changes in visceral, subcutaneous or total fat in
either of the low exercise groups for men or women, which suggest
that this amount of exercise is adequate to prevent significant
gain in fat around the stomach and that the amount of exercise
is more important than the intensity," Slentz said. "The
data emphasizes the high cost of continued physical inactivity,
the preventative abilities of modest amounts of exercise, and
the substantial benefits to be gained by performing 50 percent
more exercise each week (17 versus 11 miles per week)."
The Duke team was led
by cardiologist William Kraus, M.D., who received a $4.3 million
grant from the National Heart, Lung and Blood Institute in 1998
to investigate the effects of exercise on sedentary overweight
adults at risk for developing heart disease and/or diabetes. The
results of that five-year trial, dubbed STRRIDE (Studies of Targeted
Risk Reduction Interventions through Defined Exercise), are now
being published and presented.
Joining Slentz were
Duke colleagues, Lori Aiken, Brian Duscha, Johanna Johnson, Kevin
Ketchum, Leslie Kelly, and Kraus. Joseph Houmard, Ph.D., and Chuck
Tanner from East Carolina University, were also members of the
team.
--------------------------------------------------------------------------------
This story has been
adapted from a news release issued by Duke University Medical
Center.
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