Scientists Know that Fatty Diets Cause Blood Sugar Problems
I have to say, I agree with her. High-fat diets likely contribute to insulin resistance, and in turn, diabetes. I've read a number of studies over the years that support this link - both epidemiological and clinical studies, the latter on animals as well as humans. I don't know why this link isn't discussed much in the media.
I've also wondered whether low-carb (and so, by default, high-fat) diets disguise this problem. As long as you continue to eat very little carbohydrate, insulin resistance that a high-fat diet may be promoting might not be apparent - that is, if you're just looking at blood glucose levels.
(The rats in the study Laurie mentions, the ones that experienced insulin resistance, were eating about 50% of their calories from fat and 30% from carbohydrate. There were 2 high-fat groups: one eating flax seed and olive oil, the other lard and corn oil.)