Fats are found in vegetable oil, seeds and nuts, meat and fish, and dairy products,
as well as in foods like potato chips and french fries (that are cooked in oil), cookies, cake, and so on. There are certain fats you absolutely need to survive (the essential-fatty acids), and others you would do well to drastically limit (saturated fats) or avoid altogether (trans fats). Chemically, all fatty acids contain carbon chains with hydrogen atoms bonded to the carbon, and all fats have the highest calorie density – containing nine calories per gram (see page 43).

Until recently, the best wisdom was to eat a low-fat, low-cholesterol diet. This advice is now largely out of date. The latest research seems to show that the total amount of fat in the diet may not be strongly linked with disease. What appears to matter is the type of fat in your diet.

Saturated Fats: When all carbon bonds of a fat molecule are filled with hydrogen, a fat is said to be saturated, i.e., saturated with hydrogen atoms. Most saturated fats are animal in origin and are solid at room temperature (good examples are butter and the fat in meats). Generally speaking, you should avoid or at least severely limit your intake of saturated fats because they can raise both your total and bad LDL blood cholesterol levels which increases your chances of getting heart disease.

When hydrogen atoms are missing along the carbon chain the fatty acids are called monounsaturated or polyunsaturated depending on their exact chemical structure.

Monounsaturated fats (also called omega-9 fatty acids) are liquid at room temperature and are known as oils. They are “good fats” and are derived from plant sources, such as vegetable oils, nuts, and seeds. In studies in which monounsaturated fats were eaten in place of carbohydrates, LDL blood cholesterol levels decreased and HDL cholesterol levels increased. Monounsaturated fats are found in high concentrations in canola, olive and peanut oils.

Polyunsaturated fats are also liquid oils at room temperature and in your refrigerator. They are “good fats” and are derived from plant sources, such as vegetable oils, nuts, and seeds. Again, research has demonstrated that when polyunsaturated fats were eaten in place of carbohydrates, LDL blood cholesterol levels decreased and HDL cholesterol levels increased. Polyunsaturated fats are found in high concentrations in sunflower, soybean and corn oils.

Essential-Fatty Acids are a class of polyunsaturated fatty acids that our body cannot create. These fats must be obtained from the food you eat. Essential-fatty acids promote absorption of the fat-soluble vitamins A, D, E, and K and are also thought to provide many disease-fighting benefits. Because essential-fatty acids are needed and our body cannot manufacture them, they must come from the food we eat. Essential-fatty acids fall into two groups: omega-3 and omega-6.

Omega-3 fatty acids are relatively hard to find. Foods high in omega-3 fatty acids are walnuts, tofu, flax seeds and oily fish (salmon, mackerel, sardines, trout and albacore tuna). Omega-3 fats are thought to be heart-protective. (The American Heart Association suggests that people with coronary-heart disease consult with their physician regarding the advisability of taking a fish-oil supplement.)

Omega-6 fatty acids, on the other hand, are more common, easier to find, and are in most oils including sunflower, soybean and corn oils.

Current thinking is that the consumption of omega-6 and omega-3 fatty acids should be in the ratio of 3:1, with about three omega-6 for one omega-3. Many Western diets, however, contain about 15:1, omega-6 to omega-3, which is not good for your health. Although you need omega-6, people generally eat too much of it and not enough omega-3 fat. The American Heart Association recommends that you eat fish (particularly fatty fish) two times a week, as a way to get a more appropriate quantity of omega-3 fatty acids in your diet.