Rochester, MINN (06/13/05) - Walking to the car, climbing a few stairs
or making extra trips to the fax machine. These aren't the sort of things
you do at the gym, but each of these activities counts in terms of burning
calories and keeping weight under control. Indeed, research, published in
the journal Science
shows that lean people tend to do more of these sorts of activities throughout
a typical day than obese
people, suggesting even minor activities play an important role in burning
fat.
Such activities are called non-exercise activity thermogenesis
(NEAT), according to James Levine, MD, associate professor of medicine at
the Mayo Clinic. He is lead author of the study which showed that doing a
lot
of these activities throughout the day (without going to the gym) can burn
off
as
much as 350 calories a day.
"The effect is cumulative," Dr. Levine told Access Excellence.
Even better, it seems to be enough to ward off obesity, as long as the energy
expended
is greater than energy intake. Fat build-up occurs when energy intake
exceeds energy input. The study investigated whether there was a relationship
between body mass index (BMI) and the amount of energy people typically
expended throughout the day doing regular non-exercise activities.
BMI is
a number that reflects what body weight is like in relation to
height. The US Centers for
Disease Control (CDC)
defines underweight as a BMI of less than 18.5, normal as being
18.5 to 24.9, overweight as 25 to 29.9 and obese as 30 and above in adults.
The study included 10 lean (BMI of about 23), and
10 obese (BMI of about 33) adults who had sedentary lifestyles and did
not
do regular
exercise.
With the obese subjects, researchers selected healthy people who were
not incapacitated by their obesity.
To measure expended energy, subjects were all provided with specially designed
undergarments that were embedded with technology that measured and recorded
changes in posture. It tracked how many times people stood, sat, lay down
or walked, and for how long. Movements were measured every half second for
24 hours a day for ten days.
To control the amount of energy subjects took in diet-wise, study participants
had to eat meals that were prepared at the hospital where the research was
being done. The meals were prepared specially for the study, and the amount
people
ate
was recorded. "To do this study we provided 20,000 meals. Every single food
item was weighed to within a gram," Dr. Levine said. Subjects were told to
pursue
their normal activities for the duration of the study.
At the end of the ten day study period, researchers found that the obese
subjects sat for an average of 164 minutes per day more than their lean counterparts.
The lean people were upright (standing or walking) for an average of 152
minutes
longer than the obese subjects. People in both groups had similar types of
jobs,
and
the
amount
people slept was similar between the two groups.
The researchers reported that if the obese people had moved around as much
as the lean subjects, they would have burned an additional 352 calories per
day. "Importantly, what it represents is an extra two and a half hours of
standing and walking time, not going to the gym," Dr. Levine said. The calories
used could be sufficient to keep weight in check.
Chicken and Egg Question
The finding lead to another question, Dr. Levine said. Does being obese
cause people to tend to be less active, or does having a natural tendency
to be less active cause obesity? It's a chicken and the egg type of question.
To answer this, a second study was launched. Here, nine of the lean people
from the original study were fed an additional 1,000 calories a day for an
eight week period to see if gaining weight would cause them to become less
active. As well, seven obese subjects had a reduction of 1,000 calories
per day to help them lose weight and see if they became more active.
Among
the lean people, the average weight gain was 4 kg, and the obese subjects
lost an average of 8 kg. It turned out that neither weight gain nor weight
loss changed how much the subjects tended to stand or walk.
"These activity patterns are very, very biologically driven for a given
individual, implying that you really need to evoke substantial environmental
changes," Dr. Levine said. That is, to lose weight, people need to become
substantially more active in their daily routines. Walk more, use stairs
instead of
escalators, or walk to the coffee shop that's an extra block away. Frequent,
small amounts of activity add up.
However, losing weight is not the same as becoming fit, said Jack Goodman,
PhD, professor of exercise physiology at the University of Toronto.
He was not part of the NEAT study team. "There are many components to health
and
fitness...
obesity and weight loss is a sliver of the issue." Fitness includes good
cardiovascular health as well as strength, flexibility, and
being able to perform activities without difficulty.
"Walking around, taking the stairs, is important, but they're
not the recipe for fitness," he said. But for people who are obese, NEAT
is an excellent place to start in that it can put people on the path to better
overall health. People who are obese have an increased higher
risk for developing problems with glucose metabolism
along with
increased
risk for
diabetes.
As well, obesity increases the likelihood of having elevated "bad" cholesterol.
Losing weight can reduce these risks.
"There's a science of physical activity in what you need to do to become
fit from a cardiovascular point of view," Dr. Levine said. As people lose
weight,
it's a good idea to increase the intensity of exercise to become heart healthy,
and address other health parameters. Different types of activity provide
different types
of benefits.
end
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