A couple studies showing CLA is bunk
Effects of cis-9,trans-11 conjugated linoleic acid supplementation on insulin sensitivity, lipid peroxidation, and proinflammatory markers in obese men
QUOTE
We recently showed that trans-10,cis-12 (t10,c12) conjugated linoleic acid (CLA) causes insulin resistance in obese men. However, metabolic effects of the c9,t11 CLA isomer are still unknown in obese men. 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. 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. Design: In a randomized, double-blind, placebo-controlled study, 25 abdominally obese men received 3 g c9,t11 CLA/d or placebo (olive oil). Before and after 3 mo of supplementation, we assessed insulin sensitivity (hyperinsulinemic euglycemic clamp), lipid metabolism. body composition, and urinary 8-iso-prostaglandin F2alpha (a major F2-isoprostane) and 15-keto-dihydro-prostaglandin F2alpha, markers of in vivo oxidative stress and inflammation, respectively. Results: All subjects completed the study. Compared with placebo, c9,t11 CLA decreased insulin sensitivity by 15% (P < 0.05) and increased 8-iso-prostagiandin F2alpha and 15-keto-dihydroprostaglandin F2alpha excretion by 50% (P < 0.01) and 15% (P < 0.05), respectively. 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 F2, concentrations. There were no differences between groups in body composition. Conclusions: A CLA preparation containing the purified c9,t1 I CLA isomer increased insulin resistance and lipid peroxidation compared with placebo in obese men. Because c9,t1 I CLA occurs in commercial supplements as well as in the diet, the present results should be confirmed in larger studies that also include women.
Okay, so there's 9,11-CLA...
Supplementation with trans10cis12-conjugated linoleic acid induces hyperproinsulinaemia in obese men: close association with impaired insulin sensitivity
AU: Riserus,-U [Author,-Reprint-Author]; Vessby,-B [Author]; Arner,-P [Author]; Zethelius,-B [Author]
SO: Diabetologia-. 2004; 47(6): 1016-1019.
PY: 2004
LA: English
QUOTE
AB: Aims/hypothesis. Hyperproinsulinaemia reflects both beta cell dysfunction and insulin resistance in cross-sectional studies, but it is not known whether changes in proinsulin concentrations are related to insulin resistance over time. As trans10cis12 (t10c12)-conjugated linoleic acid (CLA) supplementation induces insulin resistance in obese men, we used this fatty acid to investigate the effects on plasma proinsulin, insulin, C-peptide and adiponectin concentrations, including their associations with change in insulin sensitivity. Methods. We randomised (double-blind) 57 non-diabetic abdominally obese men to receive either 3.4 g t10c12CLA, CLA-isomer mixture or control oil for 12 weeks. Insulin sensitivity (hyperinsulinaemic-euglycaemic clamp), intact proinsulin, insulin, the proinsulin : insulin ratio, C-peptide, glucose and adiponectin were assessed before and after supplementation. Results. Supplementation with t10c12CLA increased proinsulin (p<0.01), the proinsulin : insulin ratio (p<0.05) and C-peptide concentrations (p<0.001) in comparison with control subjects. Adiponectin, however, did not change significantly. The change in proinsulin, but not the proinsulin : insulin ratio, was related to impaired insulin sensitivity (r=-0.58, p<0.0001), independently of changes in insulin, C-peptide, glucose, adiponectin and BMI. Conversely, the correlation between insulin sensitivity and specific insulin (r=-0.46, p<0.001) did not remain significant after adjustment for proinsulin. Induced hyperproinsulinaemia was also correlated to adiponectin concentrations (r=-0.34, p<0.01). Conclusions/interpretation. In obese men, t10c12CLA induces hyperproinsulinaemia that is related to impaired insulin sensitivity, independently of changes in insulin concentrations. These results are of clinical interest, as hyperproinsulinaemia predicts diabetes and cardiovascular disease. The use of weight-loss supplements containing this fatty acid is worrying.
