I went to Sally Fallon's seminar the other night - mind blowing. Check out www.westonaprice.org Believe it or not, it's the saturated fatty acids that are good for us and protect us from heart disease and other modern diseases. Vegetable oil is poison because of what they do to it - high heat processing, bleaching, solvents, deodorising, you name it. It's back to the good old days of butter and lots of protein. Low fat vegie oil/ margarine diets is what is killing us.
I did read that she said olive oil is fattening but I think most of it comes out and it definitely is good for us! And just cleaning out your liver will improve your metabolism anyway.