Riserus U, Arner P, Brismar K, Vessby B. Treatment with dietary trans10cis12 conjugated linoleic acid causes isomer-specific insulin resistance in obese men with the metabolic syndrome. Diabetes Care 2002;25:1516-21.Sixty obese Caucasian men with metabolic syndrome (abdominal obesity, insulin resistance, dyslipidemia and hypertension) participated in a trial of CLA. Subjects were randomly assigned to receive 3.4 grams per day of CLA (mixed isomers), trans-10, cis-12 CLA, or placebo for 12 weeks. Subjects taking the trans-10, cis-12 isomer had statistically significant increases in insulin resistance and glycemia as well as reduction in HDL cholesterol. Subjects receiving the mixed CLA had lowered HDL cholesterol only. No change in weight or body composition was observed. Researchers note that change in insulin resistance was unexpected.
Blankson H, Stakkestad JA, Fagertun H, Thom E, Wadstein J, Gudmundsen O. Conjugated linoleic acid reduces body fat mass in overweight and obese humans. J Nutr 2000;130:2943-8.
Sixty volunteers with body mass index values between 25 and 35 kg/m2 were randomized into five groups to receive either 1.7, 3.4, 5.1 or 6.8 grams of CLA or 9 g placebo per day for 12 weeks. A significantly higher reduction in body fat mass (BFM) was found in the CLA groups when compared with the placebo group, however no additional effects on BFM were observed with doses higher than 3.4 grams per day. No significant differences were observed in lean body mass, blood safety variables or blood lipids. Non clinically significant changes in blood lipids, potassium, creatinine, platelets and bilirubin were observed as well. One severe case of fatigue and some mild-to-moderate gastrointestinal symptoms were reported.
Smedman A,.Vessby B. Conjugated linoleic acid supplementation in humans—metabolic effects. Lipids 2001;36:773-81.
Fifty-three healthy men and women participated in a trial of CLA and reduction in body fat. Subjects were randomly assigned to supplementation with 4.2 grams per day of CLA or placebo for 12 weeks. Subjects in the treatment arm showed a significantly decreased proportion of body fat when compared with the control group. No changes were seen on body weight, body mass index, abdominal diameter, serum lipids or glucose metabolism in the treatment group as compared to the placebo group.