Those are the results of the first U.S.-based studies in people of the effects of conjugated linoleic acid, or CLA. CLA is a popular dietary supplement commonly used to help 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.
CLA is a naturally occurring fatty acid found in many meat and dairy products. In studies in animals, it has also been shown to fight arteriosclerosis, or hardening of the artery walls, and several types of cancer. It also appears to enhance the immune system. The results of the first U.S. human studies were presented Sunday at a meeting of the American Chemical Society, the world's largest scientific society.
Michael Pariza, PhD, is director of the Food Research Institute at the University of Wisconsin in Madison, where the fatty acid was discovered and where it has now been shown to aid in weight management. "It is keeping little fat cells from getting big," explains Pariza, one of the study's lead investigators and a member of the team that documented CLA's existence in 1978.
Since that discovery, two decades' worth of study has yielded much information about the effects of CLA, he tells WebMD. The latest study simply confirms that CLA is a safe and effective option for weight management, when combined with dieting and exercise, he says.
For the study, 80 obese people were told to diet and exercise, and their weight and body composition were monitored over a six-month periods. Most lost 3-5 lb but regained most or all of that weight. However, those study participants who took CLA retained an even ratio of muscle and fat over the six months -- while those who did not take the supplement put pounds back on at the more typical ratio of 75% fat to 25% lean mass, he says.
None of the participants had any side effects that could be attributed to the treatment, Pariza adds. In fact, the CLA group suffered from fewer stomach problems and showed an overall improvement in mood as well as mental functions, Pariza says. "The results showed that CLA made it easier for people to stay on their diets," he says.
While Pariza's study did not note a weight loss benefit, a Norwegian study suggests that CLA may help people shed a few pounds. In that study, the 60 participants were not allowed to diet, but they still lost weight.
This weight loss was equal to a 160-lb person losing 2-3 lb over three months, says researcher Ola Gudmundsen, PhD, managing director of Scandinavian Clinical Research. "That doesn't sound like a lot, but it is statistically significant," he says.
Still, it is more likely that CLA simply aids with weight management, says Pariza, whose team stumbled upon CLA while searching for other molecular mutations caused by cooking meat.
CLA is a collective term for various alterations of a fatty acid called linoleic acid, which acts as a growth stimulant. But CLA seems to counterbalance some of the fat-converting activities of linolic acid, Parisa explains. CLA is found predominately in meat and dairy products, but it can also be found in human blood, tissues, and breast milk, he says.
The problem is that the CLA levels in the average person's diet appear to have declined, Pariza says. Although the substance can be derived from natural source such as lamb, which has about 6 mg per gram of fat, or homogenized milk, which contains a smaller amount, his study's results were based on an intake of far more CLA. Each day, the participants took tablets containing close to 2.7 grams of CLA, he says.
As a dietary supplement, CLA may be of most benefit to type 2 diabetics, for whom obesity is one of several major risk factors, according to other research. At the American Chemical Society Meeting on Monday, researchers at Purdue University in West Lafayette, Ind., are to detail another study in which CLA was found to help about 64% of 22 people with type 2 diabetes to control their insulin levels.
That means that CLA may at least serve as a natural alternative to drug therapy in delaying and managing this type of diabetes, says researcher Martha Belury, PhD. Belury, who is now a doctor at Northwest Hospital in Seattle, says that using CLA along with drugs may reduce the adverse effects of long-term drug use while helping to decrease health care costs.
But it is important to look for credible brands of CLA, cautions Pariza, whose team used a 'high grade' version that was more than 90% pure: "There's a lot of junk out there."