Is the cholesterol in egg yolks the "good" or "bad" kind? Can you "burn" cholesterol by exercising? Which has more cholesterol, a tablespoon of butter or a cup of peanut butter?

Most people know that fat is bad for them, but two-thirds of Americans are confused about how cholesterol differs from fats. The fat issue is actually the most clearly defined topic in nutrition. Yes, most Americans should cut the fat. They need to do it now and for the rest of their lives, for the sake of their hearts, health, and waistlines.

Cholesterol and Exercise

Can You Burn Off Cholesterol?

Cholesterol is a type of lipid, just as fats are. However, unlike fat, cholesterol can't be exercised off, sweated out, or burned for energy. It is found only in animal products, including meat, chicken, fish, eggs, organ meats, and high-fat dairy products.

Is Cholesterol Good or Bad?

Just as homemade oil-and-vinegar dressing separates into a watery pool with a fat-slick topping, so also would fats and cholesterol if they were dumped directly into the blood. To solve this dilemma, the body transports fat and cholesterol by coating them with a water-soluble "bubble" of protein. This protein-fat bubble is called a lipoprotein.

• Low-density lipoproteins (LDLs) carry cholesterol to the tissues. This is "bad" cholesterol, since high LDL levels are linked to increased risk for heart disease.
• High-density lipoproteins (HDLs) carry excess cholesterol back to the liver, which processes and excretes the cholesterol. HDLs are "good" cholesterol; The more HDL you have, the lower your risk for developing heart disease.
• HDLs and LDLs are found only in your blood, not in food.

Test Your Cholesterol

Your risk for heart disease can be assessed with a blood-cholesterol test. In this test, your total-cholesterol reading should approximate the sum of your LDL, HDL, and other lipoproteins. If you have 3.5 mg of total cholesterol, or less, for every 1 mg of HDLs, then your cholesterol ratio is ideal. According to guidelines from the National Cholesterol Education Program:

• Total cholesterol should remain below 200 mg/dL, unless HDL is high.
• LDL should be lower than 130 mg/dL.
• HDL should be 40 mg/dl or higher.

However, if you have any risk factors for heart disease, you'll want to get your LDL even lower, less than 100 is optimal.

What Are Triglycerides?

The fats that supply calories, float in your blood, and accumulate in your thighs and hips are called "triglycerides." They can be saturated or unsaturated, and the unsaturated ones can be either monounsaturated or polyunsaturated. For every ounce of triglycerides you eat, you add 250 calories (or 9 calories per gram -- the weight of a raisin) to your diet. Only saturated fats increase blood levels of cholesterol and heart-disease risk.

Which Ones Are Saturated?

In general, the harder a fat, the more saturated it is. Beef and dairy fats are mostly saturated fats. Liquid oils are usually unsaturated fats, including monounsaturated fats in olive and canola oils and polyunsaturated fats in safflower, corn, soybean, and fish oils. Coconut, palm, and palm kernel oils are exceptions to the rule; these liquid vegetable oils are highly saturated fats.

Fear of Frying

Eating foods with a lot of saturated fat raises your risk for heart disease; this causes the amount of bad LDLs in your blood to increase while good HDLs decrease. Cut the saturated fat, and your blood-cholesterol levels and your risk for heart disease drop. Your risk for cancer also decreases. A diet with more polyunsaturated fats, rather than saturated fats, lowers total blood-cholesterol levels, but unfortunately also drops HDL levels, so you lose both good and bad cholesterol. Olive oil is another story. This oil lowers total-blood cholesterol and LDL cholesterol without causing HDL levels to drop. By using olive oil, you can decrease your total-cholesterol levels while maintaining your HDL levels, thus decreasing your risk for heart disease. Fish oil also lowers heart-disease risk. Consequently, olive and fish are the oils of choice.

The Lowdown on Trans Fats

Hydrogenated fats are liquid vegetable oils made creamy when manufacturers convert some of the unsaturated fats into saturated ones through a process called "hydrogenation." This process also rearranges the molecular shape of the remaining unsaturated fats. The resulting shape is an abnormal "trans" shape.

Trans fatty acids constitute up to 60% of the fat in processed foods containing hydrogenated fats. TFAs raise blood-cholesterol levels and increase heart-disease risk just like saturated fats. Knowing your fats gives you an edge when it comes to buying and preparing the right foods to eat. And when you steer away from the saturated fat and trans fatty acids, you can live a heart-healthy life. The bottom line is:

• Eat less fat, especially saturated fat.
• Limit your intake of fatty meats, fatty dairy products, and processed foods that contain hydrogenated vegetable oil.
• Use olive oil, but in moderation if you're watching your weight.
• Fill your plate with fruit, vegetables, whole grains, fish, and legumes.

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