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Weight loss in a bottle? Forget the claims. Here's the evidence

Nutrition Action Healthletter, May, 2005 by David Schardt

If you watch television, scan the drugstore supplement shelves, or do any grocery shopping, odds are you've seen dozens of new products that promise to help you lose weight. Here's the scoop on three of them.

C-L-A-ter

"Tonalin CLA is an effective supplement that may help you decrease the amount of fat stored in your body," says the company Web site (cognis.com).

CLA, short for conjugated linoleic acid, is a mixture of fats that occur naturally in tiny amounts in meat and dairy products. It has been a substance in search of a cause ever since it was identified as a potential cancer fighter in animal studies nearly 20 years ago. (Whether CLA can prevent cancer in people is still unknown.)

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For several years CLA was touted as a weight-loss godsend, but that faded as well-designed studies failed to show that it caused significant weight loss. Now, CLA researchers and manufacturers have targeted fat loss as its main benefit.

"A lot of carefully done studies have shown that CLA can prevent fat from being stored in animals," says researcher Peter Jones of McGill University in Montreal.

"But the evidence in humans is inconsistent," he adds. In some studies CLA lowers body fat in overweight adults; in others it doesn't.

That could be because not all CLA is alike. There are some 25 different chemical forms, or isomers, of CLA, Jones points out. "These can have any of several different effects, either alone or in combination. And that could well be responsible for the different results."

Another problem: quality. When Jones tried to buy CLA wholesale for his research, he was quoted prices that ranged from $36 a pound to $5,450. "You know that the cheaper stuff is probably going to have a lot of contaminants that could affect the results."

Different purities and formulations could also explain why some researchers have seen side effects in people who take CLA.

For example, Ulf Riserus and his colleagues at Uppsala University in Sweden found that each of the two most-studied CLA isomers, taken separately, increased insulin resistance in obese men with the metabolic syndrome. (1,2) But when the men took the two isomers in equal amounts, insulin resistance didn't increase.

(CLA labels don't give a breakdown of the isomers, but Tonalin contains equal amounts of the two.)

Insulin resistance is part of the metabolic syndrome, which is a cluster of symptoms that includes elevated blood pressure, blood sugar, and triglycerides plus low HDL ("good") cholesterol and a large waist. An estimated one in four Americans has the metabolic syndrome, which increases the risk of heart attack, stroke, and diabetes.

The most comprehensive study of CLA ever conducted highlights both its promise and its potential downside.

Jean-Michel Gaullier and his co-workers in Norway gave 93 middle-aged, overweight men and women 3.4 grams a day of Tonalin CLA and told them to follow their regular diet and exercise routine. (3)

After one year, the Tonalin takers had lost, on average, five pounds of body fat while similar people who took a placebo gained close to one pound. Most of the fat was lost during the first six months.

But the Tonalin group also had higher levels of leucocytes (white blood cells), which is a sign of inflammation. And they had higher levels of both thrombocytes (blood-clotting cells) and a chemical cousin of LDL ("bad") cholesterol called lipoprotein(a). All point to an increased risk of heart disease and stroke.

"Further studies are needed to determine if there is an effect of CLA on cardiovascular risk and inflammation," concluded Gaullier and his colleagues.

"As of now, the risks are more documented and the benefits are questionable," adds CLA researcher Darshan Kelley of the U.S. Department of Agriculture's Western Human Nutrition Research Center at the University of California at Davis.

Our advice: until researchers can show that CLA works and is safe, don't try it.

(1) American Journal of Clinical Nutrition 80: 279, 2004.

(2) Diabetologia 47: 1016, 2004.

(3) Journal of Nutrition 135: 778, 2005.

CortiSlim Evidence

"Daily stress--work, relationships, bills, traffic (even dieting)--triggers a hormonal release that signals the body to store fat," says Shawn Talbott, dietary supplement executive and adjunct professor of nutrition at the University of Utah in Salt Lake City. "I formulated CortiSlim to help control this fat-storing hormone."

Actually, a California supplement manufacturer. Steve Cheng, approached Talbott to devise a weight-loss product that they and psychologist Greg Cynaumon could peddle on TV. Since 2003, the three have sold millions of dollars worth of CortiSlim. Their success has spawned dozens of "CortiCompetitors," including CortiDrene, CortiTone, CortiSol, and CortiDiet.

The hormone that CortiSlim is designed to control is called cortisol. Among its many functions: keeping blood pressure up during traumatizing events.

Weight loss in a bottle? Forget the claims. Here's the evidence

Nutrition Action Healthletter, May, 2005 by David Schardt

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