Omega-3 fat. An “essential” (meaning the body can’t make its own) fat that is good for you. Because the body can’t make it, you need to get it from your diet. Omega-3 fat protects against age-related ailments, such as heart disease, certain cancers, immune disorders, and possibly multiple sclerosis and Alzheimer’s disease. Ths best sources are cold water fish (salmon, mackerel, tuna), as well as flaxseed meal and oil. Canola and soybean oils contain small amounts of omega-3 fat.

Omega-6 fat. Another essential good fat. Most people get plenty since it is found in corn oil, sunflower and other vegetable oils. Crucial for healthy skin and proper brain function. Too much, however, can be bad for your heart. Twenty grams or fewer a day of fat should come from vegetable oils.

Monounsaturated fat. Not essential since the body produces its own, but it is a good fat as it lowers risk of heart disease by lowering cholesterol levels. Olive, canola, and peanut oils are high in monounsaturated fat.

Saturated fat. Is a "bad" fat for a number of reasons. It increases cholesterol and therefore raises heart-disease risk. It is found in butter, margarine, fatty meats, full-fat dairy products and fast foods.

Trans-fat. Formed when vegetable oils are hydrogenated (or partially hydrogenated) to make them have a longer shelf-life. Trans-fats are just as bad as saturated fats. Most prepared baked goods (cookies, crackers, cakes, doughnuts, chips, etc,) contain trans-fat.