Trans fat is an unsaturated fat. Trans fat occurs naturally in some animal foods and is present at very low levels in refined vegetable oils, but it is not essential in the diet. Trans fats are made when liquid oils are turned into solid fats, like shortening or margarine. These are called partially hydrogenated oils.

Of all the fats, trans fat is considered the worst type of fat to eat. Unlike other dietary fats, trans fats — also called trans-fatty acids — raise “bad” cholesterol and lowers “good” cholesterol. A diet laden with trans fats increases your risk for heart disease and other health problems.