Trans fat is the dietary equivalent of the devil. It provides no nutritional value, and reeks havoc on the body's ability to transport fats through the blood. In terms of the different types of fat that people obtain through their diet, the following effects take place: Saturated fat raises LDL (the bad cholesterol), but basically leaves HDL (the good stuff) in tack Polyunsaturated fat raises HDL (the good stuff), so it helps you Monounsaturated fat typically raises HDL, but sometimes raises LDL, so while it usually is good for you, in excess it can sometimes be bad for you Trans fat raises LDL ...