The supplements are widely available wherever weight-loss products are sold, including drugstores, grocery stores and Internet sites. Natrol sells 60 soft gels containing a 1-gram blend of CLA and other fatty acids for about $20. Taking one soft gel with each meal as directed, you'll end up paying about $30 for a one-month supply. Each capsule of SuperFats from Nutrabolics contains 830 milligrams of a "SuperFats" complex of CLA, sesame seed extract and Korean pine nut extract. A 120-capsule bottle -- enough for 20 days if you take three capsules two times a day with meals as directed -- costs about $30.
The claims: The packaging for Natrol's CLA says that the supplement "may help you reduce body fat and increase muscle retention." The Nutrabolics website claims that "studies have concluded that CLA is extremely effective at reducing body fat." The site also says that SuperFats "trains your body to be a better fat-burning machine, so you lose fat -- permanently."
Get developments in medicine, nutrition and fitness delivered to your inbox with our The Health Report newsletter. Sign up »
The bottom line: The history of CLA has had some ups and downs. Early excitement faded when it became clear that the supplement doesn't work as well in humans as it does in lab animals, says Leah Whigham, a researcher with the School of Medicine and Public Health at the University of Wisconsin-Madison. "It isn't as effective as a lot of people hoped," she says. "But it may still be worth a try." In addition to the potential weight-loss benefits, there's some evidence that CLA supplements can ease inflammation in the body and possibly lower the risk of cancer, she says.
Whigham was the lead author of a 2007 American Journal of Clinical Nutrition study that pooled the results of 18 previous studies investigating the effect of CLA on body fat. She and her co-authors concluded that people who take about 3 grams of CLA each day lost, on average, about 0.1 pounds of fat each week. The benefits seemed to peter out after two years -- enough time to potentially lose more than 10 pounds of fat. "It can give people a little extra boost," Whigham says. "They should still combine it with sensible eating and exercise."
CLA comes in different chemical forms or "isomers." According to Whigham, the t10, c12 isomer is the one most likely to help with weight loss.
Cynthia Heiss, a registered dietitian and member of the American Dietetic Assn. who wrote a 2003 review article of CLA in the Journal of the American Dietetic Assn., doesn't believe that CLA or any other supplement can solve anyone's weight problem. "If there was a product that worked, people wouldn't be overweight," she says.
Heiss found another option. She says she lost about 115 pounds over two years -- through healthful eating and regular exercise.
OK, so CLA isn't a miracle. But hey, what about Lipozene? Read about it here.
Is there a consumer product you'd like the Healthy Skeptic to examine? E-mail the details to email@example.com.