PUFAs Acutely Affect Triacylglycerol-Derived Skeletal Muscle Fatty Acid Uptake And Increase Postprandial Insulin Sensitivity, American Journal of Clinical Nutrition, April 2012
It was a small study in men who were obese and already insulin resistant. It compared 3 diets - high in either saturated fat (SFA), monounsaturated fat (MUFA), or polyunsaturated fat (PUFA). Blood glucose and insulin were significantly higher after the saturated fat meal than the PUFA meal.
Interesting that the PUFA meal led to higher circulating fatty acids. Resistant starch does this too, except by a different mechanism - colonic bacteria eat undigested (resistant) starch, producing fatty acids that we absorb. These fatty acids are linked to improvement in sensitivity to insulin.
The evidence for the role of fat - not just quantity of fat, but also type of fat - in the diet is growing. The more total fat and the more saturated fat one eats, the greater the risk for developing insulin resistance and diabetes, as I've seen. It's not an intuitive relationship. I first wrote about it in 2008:
Type Of Fat Eaten Affects Insulin Levels
The KANWU study found that insulin resistance worsened on a high saturated fat diet (but improved on a MUFA diet). And I summarized 3 large epidemiological studies that implicated saturated fat in the development of diabetes.
The best sources of saturated fat in our diets are dairy products (cheese, butter, cream and the like) and animal foods. The fat in plants tends to be more unsaturated, PUFA and MUFA.