If you thought saturated fat was the ultimate dietary evil, it's time for an introduction. Meet trans fats (also called trans fatty acid), another fat that's bad news. Like saturated fat, trans fats can boost your levels of LDL ("bad") cholesterol. It also lowers your HDL ("good") cholesterol. This one-two punch makes trans fats hard on your arteries -- not to mention your heart. How much do you know about trans fats? Take this short quiz to find out.