Almost as what appears to be a last ditch effort to demonize saturated fat, many are now spreading the myth that saturated fat causes insulin resistance. But is it true?
This matter seems a bit complicated. From what I can find, the studies that are often cited as “proof” that saturated fat causes insulin resistance merely show that unnatural applications of saturated free fatty acids to rat livers can produce insulin resistance in the rat livers.
While this is interesting (and horrific for the rats), it certainly doesn’t prove anything about the effects of natural dietary saturated fats in humans. So let’s look at what the studies have to say about the effects of saturated fats in human trials.
Thanks to Stephan Guyenet, I found a paper that states that until the year 2008, only one study in 15 had shown any correlation between saturated fat intake and insulin resistance. That one study, the KANWU study, ran for three months and included 162 participants. One group was fed mostly saturated fats and the other group mostly monounsaturated fats.
And despite the conclusion reached by the authors (“decreasing saturated fatty acid and increasing monounsaturated fatty acid improves insulin sensitivity”), the actual reported results were statistically insignificant. There was essentially no difference between the two groups.
Another study compared two groups (20 subjects total), one eating mostly saturated fat and the other eating mostly monounsaturated fat (along with other foods). The study concluded that there were no differences in insulin sensitivity between the two groups. (Dijk, et al., 2009)
In a 2011 study that included 417 subjects – the LIPGENE study – the authors concluded that saturated fat had no negative impact on insulin sensitivity. They also concluded that supplementation with omega-3 fatty acids improved some markers. (Tierney, et al., 2011)
In conclusion, there simply is no evidence that saturated fat contributes to insulin resistance.