When I was pregnant with Karston, I spent (too much) time in the waiting room for prenatal appointments. One of the articles I read while waiting, I think in Reader's Digest, said that a 2% reduction in dietary trans fat intake on a small sample of nurses correlated to a 54% reduction in heart disease risk! I was shocked, but ready to stop eating trans fats.
Note that trans fats are unsaturated. You know a product has trans fat if the ingredients list includes the word hydrogenated (partially or not). Hydrogenation increases shelf life, so it's popular. Unsaturated fat is easier to digest because enzymes can more easily get in to break the bonds where the fat molecule has a kink. What makes saturated fat saturated is that it has as many hydrogen atoms attached as possible (so it is saturated with hydrogen). That makes the saturated fat molecule fairly straight since the hydrogens on the outside repel each other slightly. So saturated fat is harder to break down in digestion since it doesn't have any kinks for enzymes to attack.
Anyway, it does seem odd that an unsaturated fat would be so bad. However, the trans configuration will be straighter than the cis configuration, so trans fats could be similar to saturated fats in digestion difficulty. Then I ran across Fear of margarine: The trans fat myth. This JunkScience site attacks scientific studies with poor statistics, but sometimes leaves out the important fact that the statistically-unsound study's conclusion was borne out by other studies with sound scientific methods and statistics. IOW, the identification of junk science is sound, but the targets are not always weak (just some of the studies). Now I'm unsure about trans fats ... I'll have to look for a study that was not done by the authors cited.