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NEW YORK (Reuters Health) - Supplements containing the fatty acid conjugated linoleic acid (CLA) may help the body shed excess fat, according to a new study.
CLA is a fatty acid found in beef, lamb and dairy products. Animal research has suggested that CLA can help melt away body fat, but studies in humans have yielded mixed conclusions.
The new study, published in the American Journal of Clinical Nutrition, combined data from 18 previous studies on CLA in order to analyze the body of evidence. It found that, when given at a dose of 3.2 grams per day, CLA appeared moderately effective at promoting body fat loss.
Across the studies, people who took CLA lost an extra 0.2 pounds of fat per week compared with study participants given a placebo, or inactive pill. The effect is "modest," according to the study authors, but still meaningful, considering the tendency of the average U.S. adult to gain weight with each passing year.
"The modest decrease in body fat shown in our meta-analysis could be important if accumulated over time, especially in our environment where gradual weight gain is the norm," said lead study author Dr. Leah D. Whigham, of the University of Wisconsin at Madison.
In general, she and her colleagues found, the body-fat benefits of CLA accrued for 6 months, then gradually faded.
As for why the animal fat might benefit human fat loss, Whigham told Reuters Health that CLA appears to affect enzymes responsible for body fat storage.
That doesn't mean, however, that people should start having a burger and a milkshake for every meal. High-fat animal products also contain plenty of saturated fat, which raises cholesterol and can contribute to clogged arteries.
Moreover, it would be tough to get 3.2 grams of CLA per day from food, Whigham pointed out.
A liter of full-fat milk, for example, contains about 1 gram of CLA.
There have been some concerns raised about the side effects of consuming CLA. Some studies, for instance, have suggested that the fat may promote insulin resistance, a precursor to diabetes. But other studies have either failed to show this effect, or found that CLA improves the body's use of insulin.
Research should continue to examine the safety of CLA supplements, Whigham and her colleagues conclude.
SOURCE: American Journal of Clinical Nutrition, May 2007.