How do I interpret my cholesterol lab tests? Can I burn off cholesterol through exercise?

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. 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 for men and 50mg/dl or greater for women.

Triglycerides should be lower than 150mg/dl

People under age 30 should shoot for an even lower total cholesterol of 180 mg/dl.

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.

Can you burn off cholesterol?

No. 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 primarily in animal products, including meat, chicken, fish, eggs, organ meats and high-fat dairy products.

Is cholesterol good or bad?

Both. 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. Interestingly, in a study in which calories from either carbohydrates or fats were decreased by 25% for four weeks, both groups lost about seven pounds but the reduced carbohydrate group decreased their LDL and increased their HDL more than the reduced fat group (American Journal of Clinical Nutrition 2001. 73(1)262). Over time, however, it is likely that the reduced fat group would experience a bigger drop.

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.

Can a cholesterol test predict which kids will become obese?

Scientists say such a test already works in lab rats, revealing which ones will become obese if given access to the rodent equivalent of limitless hamburgers, potato chips and fried chicken. Whether such a test will work in people remains to be proven. However, researchers say they are amazed at how similar the underlying machinery of appetite and weight gain are in rats and people.

“I think something like this could be applied to the human situation,” said Dr. Sarah Leibowitz of Rockefeller University in New York. She presented her research Monday at a meeting of the American Association for the Advancement of Science. Her research involves the link between high-fat food and weight gain. She and other scientists believe that too much fat in the diet – probably anything more than 30% of the day’s intake of calories – triggers weight gain by prompting the body to store new fat and making it crave still more fat to eat.

While such a system may have helped people survive when food was chronically scarce, it leads to rampant obesity when fat-loaded food and sugary soft drinks are cheap and available everywhere.

One approach to weight control is helping people know they have a problem before it develops. A test that reveals this, Leibowitz said, “would tell us how much we can splurge. People would like to have an early warning sign.”

In rats, this warning sign is the production of triglycerides, fats that circulate in the blood. Leibowitz raised rats on standard lowfat chow. When they got to be normal-size juveniles, she fed them a single high-fat meal, then measured their triglyceride levels. Ordinarily, about one-third of run-of-the-mill rats will have a weight problem if given a chance. Leibowitz found that rats whose triglycerides shot up the highest after the high-fat meal were also the most likely to become obese.