Not A Miracle Weight Loss Aid

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It sounds too good to be true but an increasing number of Americans are buying into the notion that a dietary supplement called conjugated linoleic acid, or CLA, can help them both lose weight and increase muscle mass.

A new study funded by the leading manufacturer of CLA suggests just that. But experts tell WebMD that the claims about the supplement far outweigh the science. The researcher who discovered CLA says that while it can help people replace fat with muscle, it is no miracle weight loss aid.

"I have been telling people for years that this is not a weight loss product," Michael W. Pariza, PhD, tells WebMD. "If someone takes CLA to lose weight but doesn't change their diet or exercise patterns they are going to be disappointed."

The Research

CLA is a natural occurring fatty acid found in meats and dairy products, 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.

Early animal studies following its identification by Pariza and colleagues in the late 1970s raised hopes that it could be used to fight human cancer.

The popular dietary supplement is now sold in health food stores and on the Internet.

In a study published last May involving 180 people who were overweight, those who took CLA for a year lost between 7 percent and 9 percent of their body fat even though they did not change their lifestyles or eating habits.

But CLA users lost only a modest amount of weight — 4 pounds during the year-long study. And the investigation did little to silence concerns about the long-term safety of the supplement. The volunteers taking CLA had changes in certain heart disease risk factors.

CLA users had slightly higher LDL "bad" cholesterol and slightly lower HDL "good" cholesterol than nonusers. And the CLA group had higher white blood cell counts and lipoprotein (a) levels — also known as lipoprotein little (a). Both are markers of inflammation linked to heart disease.

In this follow-up study, 134 of the overweight participants either continued taking CLA for another year or could start taking the supplement if they had been in the placebo group. Both groups took 3.4 grams of CLA a day and continued their normal lifestyle habits. They ate what they wanted without restricting calories and continued their usual amounts of physical activity.

The study was funded by the company that markets Tonalin CLA, the largest selling brand of the supplement. The findings are reported in the April 1 issue of The Journal of Nutrition.