Article Index > Authors > Jeff S. Volek Ph.D., R.D.

Conjugated linoleic acid (CLA) is a special type of polyunsaturated fat that has received a great deal of interest because of its potential role in health and reducing body fat. In animal studies, CLA supplementation has consistently been shown to reduce body fat. Studies conducted in humans have in some cases confirmed these effects. However, it should be acknowledged that not all CLA studies have shown consistent results.

In one of the studies that examined the effects of CLA on body fat, 52 overweight/obese men and women were randomized into a placebo group or one of four CLA groups that consumed 1.7, 3.4, 5.1 or 6.8 grams per day (divided into 3 equal doses).(1) Body weight and body composition (fat mass and lean body mass) were measured before and after 12 weeks of supplementation. Compared to placebo, three of the CLA groups lost significantly more fat mass. The 3.4 g/day group lost almost 4 pounds of fat and the 6.8 g/day CLA group lost almost 3 pounds of fat. The 6.8 g/day group also increased lean body mass by almost 2 pounds. The number of subjects in this study was relatively low but it did provide evidence of a favorable effect of CLA on body fat and lean body mass.

Next, I'll describe the results of two studies that involved a larger number of subjects which found similar benefits of CLA on body composition.

One-year study shows fat loss and lean mass increases
A study published in June 2004 in the American Journal of Clinical Nutrition examined the effects of CLA on body fat over a one year period.² A total of 180 overweight men and women were randomly assigned in a double-blind fashion to receive either 3.6 g of CLA (50:50 mixture of c9t11 and t10c12 isomers) in fatty acid form or a placebo (olive oil). Subjects were not provided with specific diet or exercise instructions, only to take the prescribed supplements. Body composition (using dual energy X-ray absorptiometry) was assessed before and after one year of supplementation to assess fat mass and lean body mass.

There were essentially no changes in body weight, fat mass or lean body mass in the placebo group.

There was a small weight loss of 2.4 pounds in the CLA group. There was also a significant 3.7 pound reduction in fat mass for the CLA group, as well as a significant 1.5 pound increase in lean body mass. Thus, without any dietary or exercise intervention, simply supplementing with 3.6 grams of CLA a day promoted loss in body weight and fat while increasing lean body mass.

During weight regain, CLA increases lean muscle gains and increases your metabolic rate
A study from the Netherlands provides another important dimension to research on CLA and body composition.³ This randomized, placebo-controlled, double-blind study examined the effects of CLA supplementation on regain of body weight and body composition in overweight subjects after they had lost weight.

Initially, a total of 54 men and women were submitted to a structured 3-week low-calorie diet to induce weight and fat loss. No supplementation was provided during this period. Then subjects went back to their normal diet and were divided into either a low dose (1.8 g CLA/day), a high dose (3.6 g CLA/day), or a corresponding placebo group. Doses were taken at breakfast, lunch and dinner for a total of 13 weeks. Body weight, body composition (using very accurate underwater weighing), and resting metabolic rate were determined at the start of the study (weekk 0), after the 3 week weight loss phase (week 3), and after 13 weeks of supplementation (week 16).

The results were somewhat surprising but favorable for CLA. As expected, subjects lost weight at week 3 (average 6.9%), which was associated with reduced fat mass, lean body mass, and metabolic rate. After 13 weeks of supplementation, some of the weight was regained in all groups as expected. CLA supplementation did not affect the amount of weight or fat regained, but both low- and high-dose CLA supplementation significantly increased regain of lean body mass compared to placebo. The increase in lean body mass also resulted in a significant increase in metabolic rate in the CLA groups. During the weight regain, metabolic rate increased by a little more than 200 kcal/day in the CLA group compared to about 140 kcal/day in the placebo group. The results suggest that CLA supplementation could be effective during weight maintenance by preventing regain of body fat and increasing lean weight gain and metabolic rate.

CLA's effect is independent of diet and exercise
Both these studies provide evidence for favorable effects of CLA on body composition that are independent of diet and exercise. The effects are relatively small, but arguably of important clinical significance. Small changes in fat and lean body mass are important, and pave the way to big changes over longer periods of time.

These studies and others show effective doses of CLA to be in the 2 to 4 grams per day range (equals 3 to 5 softgels per day assuming each softgel contains about 750 mg of CLA). Importantly, studies show that these doses are safe and not associated with an increased frequency of significant adverse responses.

The need for CLA supplementation
Can you get enough CLA in your diet to achieve beneficial effects on body composition? Probably not, at least if you eat a healthy diet. CLA is found in small quantities in beef, lamb and dairy products. The concentrations in these foods can vary widely. Usually the higher the fat content, the higher the levels of CLA (e.g., whole milk has more CLA than skim milk). The usual intake of CLA for people who regularly eat beef is estimated to be a little more than 200 mg/day and about half that for people who avoid beef. The doses used in studies that show improved fat loss use levels that are 10 to 30-fold higher than that typically obtained in the diet, underscoring the need to use dietary supplements in order to achieve effective doses.