CLA: The New Miracle Weight Loss Pill?

Reviewed by Michael W. Smith, MD on May 24, 2004
From the WebMD Archives

May 20, 2004 -- Conjugated linoleic acid (CLA) is a contender for the weight-loss miracle pill. One group of overweight women lost 9% body fat in one year's time. Not bad, since they didn't change their lifestyle or eating habits.

"We really believe this is promising," lead researcher Jean-Michel Gaullier, PhD, with the Scandinavian Clinical Research Group, tells WebMD. His study appears in the June issue of the American Journal of Clinical Nutrition.

"It is the first time we have looked at the effects of CLA on body composition to get unequivocal results," he says.

But here's one concern: The volunteers taking CLA had changes in certain heart disease risk factors. But Gaullier tells WebMD that the changes seen in cholesterol level and blood sugar levels were not significant.

However, the findings warrant further investigation, says Cindy Moore, MS, RD, director of nutrition therapy at The Cleveland Clinic and a spokeswoman for the American Dietetic Association. She agreed to comment on Gaullier's findings.

"The impact [of CLA] on heart disease and diabetes needs to be investigated further," Moore tells WebMD. "This is what science is all about, piecing together studies that provide the bigger, broader picture."

What Is CLA?

CLA is a naturally occurring fatty acid found in meat and dairy products. It is also a popular dietary supplement that is sold with claims of helping people lose fat, maintain weight loss, retain lean muscle mass, and control type 2 diabetes -- the type of diabetes that is often associated with obesity.

In health food stores, CLA is sold as a pill or as a syrup. The syrup tastes pretty good and can be mixed with food, Gaullier tells WebMD. "But if you break the capsules apart and try to mix it with yogurt, it tastes very bad. It has a very bitter taste."

CLA comes in varying concentrations. Be sure to buy a product containing 80% CLA to get maximum weight-loss results, he says.

In small studies involving animals, CLA has been shown to prevent heart disease and several types of cancer, Gaullier says. It also appears to enhance the immune system.

Smaller studies of CLA's effectiveness in weight loss have shown some contradictory results -- possibly because they used body fat scales to measure improvements, and those scales are not very accurate, he tells WebMD. In his study, Gaullier used a body-scanning technology called DEXA (dual-energy X-ray absorptiometry). "It is very accurate in measuring body fat," he tells WebMD.

His is the first long-term study of CLA's safety and effectiveness in weight loss.

Some Weight Loss, Excellent Body Fat Loss

Gaullier's study involved 180 overweight men and women, all between 25 and 30 BMI (body mass index). A BMI -- an indicator of body fat -- over 25 has been linked to an increased risk of heart disease and other medical problems, such as diabetes. The volunteers were mostly female -- 149 women and 31 men.

They were randomly assigned to three groups. The two groups taking CLA got either the typical off-the-shelf pills (4.5 grams of 80% CLA) daily or the syrup formulation (3.6 grams of 76% CLA disguised in a capsule) daily. The third group took a placebo capsule filled with olive oil daily.

Volunteers were not required to change their diet or exercise habits. However, a nurse did give dietary and exercise advice upon request. Daily calorie intake was similar among the three groups; all volunteers reduced their calorie intake a little during the study, he reports. All got about the same amount of exercise.

"This strongly suggests that the observed effects of CLA on body composition were independent of diet," he writes. The decreased calorie intake may be partly due to the supplements and/or a reduced appetite. Also, because volunteers kept a food diary, they "learned" to cut food intake.

Several times during the 12-month study period, volunteers came to a clinic to have their weight, BMI, and blood checked. They also completed questionnaires on their diet and exercise in the previous two weeks.

At the end of one year:

  • Both CLA groups lost weight -- about 4 pounds; the placebo group stayed the same.
  • The CLA syrup group had a 9% body fat loss; the CLA pill group had 7% loss; the placebo group had no body fat loss.

  • Both CLA groups had similar improvements in muscle mass.

As for the weight loss, "any weight loss is better than no weight loss -- and at least they didn't gain weight," Moore says. "But I'm interested in the fact that CLA is found naturally in certain foods [like beef, lamb, and dairy products]. Do we really need to take a supplement?"

Regarding other risk factors:

  • The CLA pill group had slightly higher LDL "bad" cholesterol.
  • The CLA syrup group had slightly lower HDL "good" cholesterol.

  • Both CLA groups had higher lipoprotein levels, a marker of inflammation and heart disease.

  • Both CLA groups had higher levels of leptin, a hormone thought to be a heart disease marker.

  • Both CLA groups had higher white blood cell counts, which could trigger damaging artery inflammation.

  • The CLA groups had only modest changes in blood sugar levels, a marker for diabetes.

Few volunteers dropped out of the study, indicating that the CLA supplements had no bothersome side effects, reports Gaullier.

"The results of this study corroborate and expand on the findings of the previous short-term studies," he writes. His results show that "the effect is greatest in those with highest body mass index," especially women with a 25 to 30 BMI.

'Normal' Changes in the Body

As far as the heart disease risk factors, the variations seen in the CLA groups "are within normal physiological range," Gaullier tells WebMD. Increased white blood cells may reflect the heightened immune response that other studies have shown. In studies in Holland, CLA has been shown to prevent some viral infections.

"CLA has also shown promise in animal studies in preventing atherosclerosis [hardening of the arteries]," he says.

The increased lipoprotein levels may be a byproduct of fat loss, says Gaullier. "The body does show inflammation caused by the process of eliminating fat. We think this is what is happening, but we don't know for certain."

"The mechanism(s) by which CLA decreases body fat mass and increases lean muscle mass is not completely understood," he writes. "CLA is known to accumulate in tissues of animals and humans where it is readily metabolized." CLA may trigger fat cell death, shrink fat cells, or it may speed up metabolism to promote weight loss, he explains.

Show Sources

SOURCES: Gaullier, J. American Journal of Clinical Nutrition, June 2004. Cindy Moore, MS, RD, director of nutrition therapy, The Cleveland Clinic; spokeswoman, American Dietetic Association. WebMD Medical News: "Supplement Can Help Manage Both Weight and Diabetes."

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