Diet Without Exercising Lose Valuable Muscle Mass

[John A. Casler]

Jamie Carruthers
SUPERTRAINING
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Relevant to previous discussions:

Older People Who Diet Without Exercising Lose Valuable Muscle Mass
ScienceDaily (Sep. 22, 2008) - A group of sedentary and overweight
older people placed on a four-month exercise program not only became
more fit, but burned off more fat, compared to older sedentary people

www.sciencedaily.com/releases/2008/09/080917095349.htm

The new study also showed that when older people diet without
exercising, they lose more lean muscle compared to those who
exercise, said senior researcher Bret H. Goodpaster. When they
combined weight loss with exercise, it nearly completely prevented
the loss of lean muscle mass. The results are important because older
people tend to lose muscle mass as they age and too much muscle loss
may interfere with activities of daily living.

The study, "Separate and combined effects of exercise training and
weight loss on exercise efficiency and substrate oxidation," appears
in the current issue of the Journal of Applied Physiology, published
by The American Physiological Society. Francesca Amati, John J. Dube,
Chris Shay and Goodpaster, all of the University of Pittsburgh,
carried out the study.

Study looks at exercise efficiency
The researchers wanted to know the best way to get better (more
efficient) at completing a defined exercise task. In particular, they
wanted to know if greater fitness could be achieved through exercise
training, weight loss (through dieting), or both. In addition, they
wanted to know which fuel source the body would draw upon,
carbohydrates or fats, under these different conditions.
The 64 participants were 60-75 years of age and were either
overweight or obese. All of the participants were sedentary at the
outset of the study. The researchers divided the participants into
three groups:

exercise only
diet only
exercise plus diet

Those who exercised could either walk on a treadmill or ride a
stationary bicycle, although most chose to walk. The dieters reduced
their caloric intake to achieve a 10% weight loss by the end of the
four-month study period. The final group combined both the daily
exercise and the diet.

Exercise increases efficiency, burns more fat
The researchers measured how many calories the participants expended
during a set work load on a stationary bicycle at the beginning and
at the end of the experiment. They found that the:

1. Exercise group expended fewer calories (became more efficient) on
the exercise task at the end of the study compared to the beginning.
2. Exercise group drew more on fat stores as the source of their
body's fuel.
3. Diet-only group did not gain efficiency in performing the
exercise task, even though they weighed less at the end of the
experiment.
4. Diet-only group's weight loss resulted from a loss of both muscle
and fat.
5. Exercise plus diet group was the most efficient at the exercise
task at the end of the experiment. This shows an additive effect of
both dieting and exercise, but most of that benefit was due to
exercise.
6. Exercise plus diet group, like the exercise-only group, drew more
on fat stores as an energy source.

"The take-home message is that, even among older people and during a
fairly short period of time, exercise produces metabolic changes that
require the expenditure of fewer calories during physical activity,"
Goodpaster said. Exercise also allowed older people to more
preferentially burn fat, which may be healthier metabolically."

Journal reference:
1. Amati et al. Separate and combined effects of exercise
training and weight loss on exercise efficiency and substrate
oxidation. Journal of Applied Physiology, 2008; 105 (3): 825 DOI:
10.1152/japplphysiol.90384.2008

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Jamie Carruthers
Wakefield, UK


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