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CLA Burns Body Fat First
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One bodybuilding supplement lately has captured the
attention of both researchers and athletes. It's CLA,
short for conjugated linoleic acid. Linoleic acid belongs to a family of
essential fatty acids called omega-6 fatty acids and performs a number of
important metabolic functions in the body. Whereas linoleic acid is present in
many vegetable oils, CLA occurs primarily in beef and dairy products. Its
commercial form is derived from sunflower oil.
CLA
has a slightly different molecular structure than linoleic acid. This variation
profoundly affects its function and gives CLA nutritional benefits different
from those of regular linoleic acid. CLA's popularity among athletes stems from
the supplements ability to augment muscle mass and burn body fat. Scientists,
however, foresee broader applications. So far, lab tests show that CLA is a
powerful antioxidant,1 benefits the immune system,2 and
has anticarcinogenic properties.3
The scientists who made these discoveries also received patents to use CLA in
livestock to improve feed efficiency, promote growth and prevent the muscle
wasting associated with steroids. Indeed, animal studies indicate that
CLA increases lean muscle tissue and burns body fat.4 More recent
human studies suggest CLA can work as a muscle-building supplement and
thermogenic (fat-burning)
aid.
Scientific
Muscle
Two animal studies presented at the 1997 Federation for Applied Science and
Experimental Biology (FASEB) national meeting in New Orleans showed CLA may help
reduce body fat and pointed to a possible mechanism for how it works.
In the first study, scientists from the University of Wisconsin in Madison found
that mice fed a regular diet and supplemented with CLA during a six-week period
gained substantially less body fat (65 to 73 percent) than the control group.
The dose, 2.5 mg per calorie of food intake, translates to about 6 g for someone
with a 2,500-calorie diet. One explanation for the fat reduction is that the
treatment animals lowered their voluntary food intake by 9 to 13 percent.
Despite this, the CLA-fed mice actually maintained a higher level of energy
expenditure than the control mice.5
The second study, conducted by Michael Pariza, Ph.D., also at the University of
Wisconsin, looked at the effect of CLA on fat metabolism. The results of his in
vitro study indicated that CLA reduces fat deposition in fat cells and increases
fat breakdown in muscle cells.6
The first two human studies on CLA supplementation were recently reported. At
the 1997 National Strength and Conditioning Association conference in Las Vegas,
Richard Kreider, Ph.D., of Memphis State University in Tennessee, presented his
study of CLA supplementations effects during resistance training on catabolism
(tissue breakdown), body composition and strength. In a double-blind manner,
researchers randomly assigned 27 experienced resistance-trained males to
supplement their diets for 28 days with capsules containing either an olive oil
placebo or CLA. Fasting blood samples, total body mass and dual-energy X-ray
absorptiometry determined body composition. Bench-press and leg-press tests on
days zero and 28 measured strength.
After the 28-day supplementation period, researchers found no differences
between the two groups in gross measures such as body weight, fat mass or
fat-free mass. However, further analysis showed that the CLA group increased
their overall strength for bench press and leg press by almost 30 pounds, while
the placebo group improved by only 9.5 pounds. Though not statistically
significant, these changes could indicate a trend. In addition, differences in
the ratio of blood urea nitrogen to creatinine--a marker of anabolic (tissue
building) vs. catabolic (tissue breakdown) status--suggested a potential net
anabolic effect.7 A longer supplementation period might lead to
statistically significant differences.
CLA For
Nonathletes
Researcher Erling Thom, Ph.D., from Medstat Research Ltd., in Lillestrom,
Norway, conducted such a study. His randomized, placebo-controlled, double-blind
trial on 20 healthy people lasted three months. Researchers measured subjects
body weight and percent of body fat at baseline, then every four weeks
thereafter. Each day, the treatment group took slightly more than 1 g of CLA at
breakfast, lunch and dinner. The other half took a placebo. The average weight
of the 10 who took CLA dropped by about five pounds (not enough to reach
statistical significance), but the body-fat percentage dropped by 15 to 20
percent, or from 21.3 percent of average body fat to 17 percent of body fat (p
< 0.05). Meanwhile, the group taking a placebo had little change.
Half the people in the study were men; half were women. Two dropped out because
of unpleasant gastrointestinal upsets. Of these, one was from the placebo group,
the other from the CLA group.8
The positive results from this pilot study lay the groundwork for future
research on different patient populations, such as people with obesity.
Although scientists arent yet sure how CLA works, they have developed three
theories.
1) CLA may directly affect fat metabolism. By preferentially burning fat and
sparing muscle glycogen, muscle mass is preserved at the expense of fat stores
during exercise and fasting.
2) It may also negate or counteract the adverse effects of hormones such as
corticosteroids. Overtraining, severe illness and other stresses cause cortisol
levels to rise. This adrenal gland hormone elevates blood sugar levels, breaks
down muscle protein, and increases fat deposition.
3) CLA
may increase production of prostaglandin E1,9 a type of fatty
acid that increases brain levels of the hormone somatotropin--which may give
athletes an advantage.10 Somatotropin increases growth hormone output
that, in turn, increases muscle growth. Prostaglandin E1 also increases blood
flow to the muscles, brain and other organs.11
However CLA works, preliminary data suggest it may help people, particularly
athletes, who need to burn fat while preserving muscle mass. Research indicates
an ideal daily dose of CLA ranges from 0.01 to 2 percent or more of daily
caloric intake.12 One study proposes that an effective dose for a
165-pound person is 3-5 g/day.13
Doses of this magnitude require supplementation. Most people ingest less than 1
g/day of CLA from food sources, which are largely limited to meat and dairy. For
example, cheese averages 2.9 mg-7.1 mg of CLA per gram of fat. A 3 g CLA dose
requires eating several pounds of cheese a day. That is s a lot of unwanted dietary
fat, so it makes more sense to take CLA supplements.
Before people begin buying all the CLA off the health-store shelves, though,
more research must be done on athletes--and the rest of the population.
References
1. van der Berg, J., Cook, M., et al. Lipids, 73: 595-98, 1995.
2. Cook, M. Poultry Science, 72: 1301-05, 1993.
3. Chin, S. Journal of Food Composition and Analysis, 5: 185-95, 1992.
4. Chin, S., et al. Journal of Nutrition, 124: 2344-49, 1994.
5. West, D. FASEB Journal, 11(3): A599, 1997.
6. Pariza, M. FASEB Journal, 11(3): A139, 1997.
7. Ferreira, M., Kreider, R., et al. Journal of Strength and Conditioning
Research, 11(4): 280, 1997.
8. Erling, T. Medstat Research Ltd., Lillestrom, Norway, July 1997.
9. Williams, L. C. L. A.: 7-9. Pleasant Grove, UT: Woodland
Publishing, 1997.
10. Dray, F. Advanced Prostaglandin and Thromboxane Research, 8: 1321,
1980.
11. Rudofsky, G. In Sinzinger, H., (ed). Prostaglandin E1 in
Atherosclerosis: 49. New York: Springer Verlag, 1986.
12. Pariza, M. U.S. Patent 5,385,616.
13. Ip, C. Cancer Research, 54: 1957s-59s, 1994.
Edmund R. Burke, Ph.D., is an associate
professor of biology at the University of Colorado, Colorado Springs, and the
author of Pyruvate (Keats, 1997). Burke is also director of sports
sciences for the U.S. Cycling Team.
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