There were no differences between groups in body composition.Ĭonclusions: A CLA preparation containing the purified c9, t11 CLA isomer increased insulin resistance and lipid peroxidation compared with placebo in obese men. The decreased insulin sensitivity was independent of changes in serum lipids, glycemia, body mass index, and body fat but was abolished after adjustment for changes in 8- iso-prostaglandin F 2α concentrations. Compared with placebo, c9, t11 CLA decreased insulin sensitivity by 15% ( P < 0.05) and increased 8- iso-prostaglandin F 2α and 15- keto-dihydro-prostaglandin F 2α excretion by 50% ( P < 0.01) and 15% ( P < 0.05), respectively. Results: All subjects completed the study. Before and after 3 mo of supplementation, we assessed insulin sensitivity (hyperinsulinemic euglycemic clamp), lipid metabolism, body composition, and urinary 8- iso-prostaglandin F 2α (a major F 2-isoprostane) and 15- keto-dihydro-prostaglandin F 2α, markers of in vivo oxidative stress and inflammation, respectively. Objective: We investigated the effects of c9, t11 CLA supplementation on insulin sensitivity, body composition, and lipid peroxidation in a group at high risk for cardiovascular disease.ĭesign: In a randomized, double-blind, placebo-controlled study, 25 abdominally obese men received 3 g c9, t11 CLA/d or placebo (olive oil).
Because c9, t11 CLA is the predominant CLA isomer in foods and is included in dietary weight-loss products, it is important to conduct randomized controlled studies that use c9, t11 CLA preparations. However, metabolic effects of the c9, t11 CLA isomer are still unknown in obese men. Background: We recently showed that trans-10, cis-12 ( t10, c12) conjugated linoleic acid (CLA) causes insulin resistance in obese men.