A Healthnotes Newswire Opinion

By Jane Hart, MD

Healthnotes Newswire (July 26, 2007)—According to a new meta-analysis, conjugated linoleic acid (CLA) may cause modest, short-term loss of body fat in certain people, but unanswered questions about the safety of long-term use indicate that it’s premature to embrace it as the new go-to supplement for weight loss.

CLA is a fatty acid that has been shown to reduce body fat in animals, although its effect on human body fat has been unclear. The meta-analysis, published in the American Journal of Clinical Nutrition, reviewed 18 studies, in order to determine whether supplementing with CLA reduces human body fat.

Results showed that people supplementing with an average of 3.2 grams per day of CLA lost a modest but significant amount of body fat: about 0.2 pounds per week compared with those people who took placebo (olive or safflower oil in most studies).

But the meta-analysis had its limitations: studies reviewed were of short duration (making the long-term effects of CLA unclear), and included other interventions, such as diet and exercise, that potentially contributed to weight loss, thereby calling the study results into question. The authors also state that it is unclear how much CLA a person has to take during what length of time to achieve optimal body fat loss. They concluded that it is not possible to draw conclusions about the effects of CLA on long-term weight maintenance.

CLA has several different chemical structures (called isomers), and certain isomers may be more effective in reducing body fat in humans than other isomers, as has proven true in animal studies, but further research is needed. The authors report that CLA was not associated with severe adverse effects in the studies they reviewed but there have been reports of CLA adversely affecting several risk factors for chronic disease.

“In clinical trials, supplementation with CLA has produced various unwanted effects, including increases in serum cholesterol levels, insulin resistance, and markers of inflammation. Additional research is needed regarding long-term safety of CLA before its routine use can be recommended,” said Healthnotes Chief Science Editor Alan Gaby, MD, an expert in medical nutrition.

People who are overweight or obese often turn to supplements such as CLA in hopes of losing weight or maintaining a healthy weight after weight loss. Healthcare professionals advise that it is important to understand the risks and benefits of dietary supplements and often recommend instead that people looking for safe, long-term weight loss focus primarily on modifying lifestyle behaviors such as diet and exercise.

(Am J Clin Nutr 2007;85:1203–11)

Jane Hart, MD, board-certified in internal medicine, serves in a variety of professional roles including consultant, journalist, and educator. Dr. Hart, a Clinical Instructor at Case Medical School in Cleveland, Ohio, writes extensively about health and wellness and a variety of other topics for nationally recognized organizations, Web sites, and print publications. Sought out for her expertise in the areas of integrative and preventive medicine, she is frequently quoted by national and local media. Dr. Hart is a professional lecturer for healthcare professionals, consumers, and youth and is a regular corporate speaker.

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