Omega-6 conjugated linoleic acid (CLA) decreased body fat and increased lean muscle in two studies.
In a body-fat study, researchers from the University of Wisconsin School of Medicine and Public Health in Madison reviewed 15 double-blind randomized placebo-controlled studies where participants took a median dose of 3.2 grams of CLA per day for anywhere from six months to two years. Doctors found that participants lost an average of 0.2 pounds of body fat per week or 0.8 pounds of body fat per month, which is approximately 10 pounds of body fat per year. The scientists noted that losing body fat usually translates to losing more total body weight, which includes fat, muscle and water, and concluded that participants who took CLA lost a modest amount of body fat.
In a lean muscle study, researchers from the Department of Nutrition in the School of Medicine and Public Health at the University of North Carolina, Chapel Hill recruited 48 obese but otherwise healthy participants, 13 men and 35 women, who took 3.2 grams of CLA per day, 6.4 grams of CLA per day or a safflower oil placebo for 12 weeks. At the end of the study period, those who had taken the 6.4 gram CLA dose had gained 1.4 pounds more muscle (lean body mass) compared to the start of the study. There were no significant changes in lean body mass for those who took the 3.2 gram CLA dose or the placebo. Participants reported no serious side effects, although markers for inflammation in the blood increased but remained within normal limits. Doctors concluded that CLA may increase lean body mass in those who are obese.