Trans Fats are by far the most harmful type of fat. The Mayo Clinic refers to trans fat as a "cholesterol double whammy" because trans fat both raises your LDL ("bad") cholesterol and lowers your HDL ("good") cholesterol. A high LDL cholesterol number in combination with a low HDL number significantly increases your risk for coronary heart disease.

In addition, trans fats have been shown to potentially increase triglycerides, increase Lp(a) lipoprotein, and to increase inflammation by damaging the cells lining your blood vessels, all of which increase your risk of heart disease.