Fats: Types of Fat

Fats come in different types. While you will want to keep them all low in your diet, it is useful to know that different fats affect your health differently. First, let's introduce the kinds of terms used to describe different fats.

Saturated fat. The term saturated fat refers to the fact that the fat molecule-which is a long chain of carbon atoms, rather like a string of beads-is completely covered (i.e., saturated) with hydrogen atoms.

Saturated fats are easy to spot because they are solid at room temperature. A cup of lard, for example, is a waxy solid, unlike liquid vegetable oils, which are low in saturated fat. Doctors and dietitians are concerned about saturated fat, because it stimulates the body to make more cholesterol and is linked to breast cancer and diabetes.

Animal products—beef, chicken, fish, most dairy products, and eggs—contain large amounts of saturated fat. This is one of many good reasons for avoiding them. A few vegetable oils, called tropical oils, are also high in saturated fats. These include palm oil, palm kernel oil, and coconut oil.

The following chart shows the percentages of saturated fat in different kinds of fat:

Trans Fats and Hydrogenated Oils. Hydrogenated oils are liquid oils that have been chemically hardened to make them more solid. They are often used in snack foods because of their very long shelf life. Unfortunately, they raise cholesterol levels and are as unhealthful as typical animal fats.

Unsaturated fats. If a fat molecule is not entirely covered with hydrogen atoms, it is called unsaturated. If there is just one spot on the molecule where hydrogen atoms are missing, it is called monounsaturated. If there are several spots where hydrogen atoms are missing, it is called polyunsaturated.

Monounsaturated fats (think of olive or canola oil) are liquid at room temperature, but solid in the refrigerator. Polyunsaturated fats (think of corn, safflower, soybean, or sunflower oils) are liquid, both on the shelf and in the refrigerator.

All fats are mixtures. Beef fat contains a mixture of saturated and unsaturated fats in roughly a 50:50 ratio. Chicken fat is about one-third saturated fat, with the rest being various types of unsaturated fats. Fish fats range from 15 to 30 percent saturated fat. And even though olive oil is mostly monounsaturated fat, about 13 percent of it is plain old saturated fat.

So even though vegetable oils are much lower in saturated fat, compared to animal fats, they are not free of them. Also, all fats are very dense in calories. It makes sense to keep them all to a minimum.