And what about the studies that showed CLA to reduce insulin sensitivity?The only studies that have ever shown a reduction of insulin sensitivity in humans after CLA supplementation have been from the use of single isomers of CLA. (23,24) As it was explained earlier, an equal mix of the two CLA isomers has been shown to be safe & effective for humans, without posing any risk for decreasing insulin sensitivity. (25) In fact, multiple human studies have shown that a 50/50 mix of the c-9, t-11/t-10, c-12 isomers actually increase insulin sensitivity. (26-28) It's been hypothesized that the two aforementioned CLA isomers have a unique antagonistic relationship, thus preventing any possible negative effect on insulin metabolism when used together in a 50/50 ratio. (24)
Chalk up another health benefit for CLA!
What about the studies that say CLA is ineffective for fat loss?
Take this quote from the 2007 CLA study analysis by Leah D Whigham et al.
"Our findings indicate that the 10 human studies that showed no statistically significant effect of CLA on fat mass lacked statistical power because the treatment duration was too short, there were too few subjects, or both. For example, based on the average difference in change in fat mass of 0.09 kg/wk between CLA treatment and placebo, the expected difference at 12 wk would be 1.1 kg. Because the average SD for within-individual change in fat mass was 2.6 kg, it is estimated that it would require 44 participants in each group to have an 80% power to detect this change with a P _ 0.05"