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What are fats?

Fats are compounds made up of fatty acids that are insoluble in water. They are found in both animal and vegetable products, and can be either solid or liquid. Meat fat, butter, margarine, and cooking oils are familiar examples.

Dietary fats are grouped according to their degree of saturation, which refers to how many atoms of hydrogen they carry. Saturated fats

have the maximum number of hydrogen atoms and polyunsaturated fats have the least number. In between, are monounsaturated fats.

Most saturated fats tend to be hard at room temperature. The major exceptions are coconut, palm, and palm kernel oil. Monounsaturated fats are soft, and polyunsaturated fats are liquid.

All fats have the same amount of calories — about 9 per gram (compared with 4 per gram for carbohydrates and protein). Hence, a diet high in fats is more likely to result in weight gain than a diet made up mostly of carbohydrates and protein.

For people who have high levels of blood cholesterol, the type of fat in the diet is as important as the amount. For example, saturated fats tend to raise blood cholesterol, while mono- and polyunsaturated fats lower it.

Why are fats important to nutrition?

Although fats have received "bad press" in recent years, they play an essential role in human nutrition. Specifically, fats are needed to:

• Provide a portion of the calories used in basal metabolism

The typical diet should include only a small amount of high-fat foods such as the above.

• Add flavor, aroma, and texture to foods.
• Promote feelings of satiety to control appetite.
• Form reserves of body fat, which can be utilized in times of need.
• Transport fat-soluble vitamins (A, D, E, and K) in the body.
• Supply the fatty acids that are essential to proper growth, metabolism, and other body processes, including the manufacture of sex hormones and cell membranes.

How much fat do I need?

Since the body can convert protein and carbohydrates to fat, only a small amount of fat is needed in the diet. About a tablespoon a day of mostly polyunsaturated fat provides all of the essential fatty acids.

The American Heart Association and American Cancer Society, as well as the Federal Dietary Guidelines for Americans, recommend that no more than 30 percent of calories come from fats, and that no more than 10 percent come from saturated fats. Since the typical American diet now derives about 40 percent of its calories from fat, it's safe to say that most people could benefit from cutting down on fats, especially those from red meats and the tropical oils.

What happens if I don't get enough fat?
The body requires only a small amount of fat in order to metabolize vitamins that are not soluble in water, namely vitamins A, D, E, and K. Deficiencies of these fat-soluble vitamins can develop in people who consume a very low-fat diet, even though adequate amounts of the vitamins themselves are consumed.

Babies who do not get enough fat do not grow properly, and they may develop liver and skin abnormalities. An infant also needs a certain amount of fat for proper brain and nerve development. It should be noted, however, that most American adults get more than enough fat. In fact, it would take a year or more to develop problems from a totally fat-free diet.

What happens if I get too much fat?
Since fat is a concentrated source of calories, weight gain is the most immediate consequence of overconsumption. The typical American diet provides more fat than most nutritionists believe is healthy, which helps account for the high rate of obesity in the U.S.

Excessive fat intake, especially of saturated fats, is linked to elevated blood cholesterol levels — a major cause of heart disease in most developed countries. A high-fat diet is also linked to development of some cancers.

Should I take a fat supplement?
No. The typical diet provides more than enough fat. Some food faddists recommend taking supplements of linoleic acid, an essential fatty acid. But a small amount of polyunsaturated fat provides adequate linoleic acid, so there is no need for a supplement.

Omega 3 fatty acids, which are found in many cold-water fish, also are available as supplements, and are widely promoted as cholesterol-lowering agents. These oils don't appear to have as much effect on cholesterol as once thought, but they suppress normal blood clotting. Thus, they should be taken only under a doctor's supervision.

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