Good Cholesterol, Bad Cholesterol

Q. How does exercise lower cholesterol? What activities are the most effective?

A. For the record, cholesterol in the body is a good thing—it is needed for cell membranes and the production of hormones, among other functions. But too much can signal that there is too much fat in the blood. Back in the ’80s when people became of aware of the need to control their cholesterol levels, many did so by shunning eggs since they contain a large amount of the substance. However, eggs are not a problem. The body makes what cholesterol it needs; the more that comes from food, the less the body makes. So cholesterol levels are controlled automatically. But a diet high in saturated and trans fats, typical of someone who eats lots of unhealthy food, may overload the body beyond its ability to regulate its levels.

Cholesterol levels reflect the amount of fat being carried through your blood by different “lipoproteins.” These numbers are used as a measure to predict your risk for heart disease. Your total cholesterol number is not as important as the figures for each of the components: your LDLs, HDLs and triglycerides.

High-density lipoproteins (HDLs) are considered to be beneficial since they sweep the blood of excess fat and cholesterol. On the other hand, low-density lipoproteins (LDLs) are worrisome because they can contribute to the build-up of plaque in your arteries. Recent research shows that the size of each of these particles is as important as the number. So with LDLs, if they are bigger and fluffier they are less likely to contribute to plaque than the smaller and denser variety. (The type of blood test to ascertain size is not often performed in a regular check-up, however.)

Experts agree that out-of-whack cholesterol, especially LDL at or above borderline levels, needs to be treated to lower the risks of heart disease. Doctors recommend an LDL level below 100 mg/dL (milligrams per deciliter of blood.), and below 70 mg/dL for those with other risk factors. Triglycerides should be below 150 mg/dL, and “good” cholesterol, HDLs, should be kept high, above 40 mg/dL and more than 60 mg/dL optimally. To find out more check out: http://www.nhlbi.nih.gov/health/public/heart/index.htm#chol

People with Type 2 diabetes or existing heart disease may need to lower their cholesterol right away, so doctors usually prescribe a quick fix, statins such as Lipitor and Zocor. At their highest doses, these potent pharmaceuticals have the ability to lower “bad” cholesterol from 20 percent to as much as 60 percent in just a few months. But even when statins are prescribed, lifestyle changes—better diet and more exercise—are an integral part of long-term management.

Diet guidelines are to reduce the main culprits: saturated animal fats (like high-fat meat and dairy) and trans fats (hydrogenated oils) in foods. A recommended diet should have less than 35 percent total fat with less than 7 percent of that saturated fat and minimal trans fat. Eating plenty of fruits, vegetables, grains and “good” unsaturated fats, such as those found in nuts, can also help lower LDLs and boost HDLs. A high soluble-fiber diet, the kind of fiber found in oatmeal, psyllium supplements and dried beans, can lower LDLs, too.

One problem with fighting high cholesterol with diet only is that even if LDLs decrease, HDLs may drop, too. Keeping HDLs high is important because it is estimated that for every 1 mg/dl increase in HDL, the risk for coronary heart disease is reduced by up to 3 percent. But doing aerobic exercise along with diet changes can prevent or decrease a drop in HDLs.

Exercise alone works to a degree, too. The biggest effect of exercise on improving  cholesterol levels is boosting HDLs and lowering triglycerides. But to give HDL levels a good boost above the baseline, exercise must be regular and expend enough energy to burn at least 800 to 1,200 calories per week. Any aerobic exercise—from walking and running to swimming and cycling—counts. Walking at three miles in an hour burns about 300 calories, on average. To meet the threshold then, a person needs to walk around eight to 12 miles a week, or do some other aerobic activity for at least 30 minutes on six or more days per week.

As far as triglycerides go, exercise can reduce them by around 15 percent to 25 percent. There appears to be a similar threshold of regular exercise required to trigger the effect—expending at least 1,200 calories a week, with up to 2,500 to 3,000 calories a week recommended.

How fitness affects LDLs is less clear. Reductions from 5 percent to 19 percent have been seen, but often with concurrent weight or fat loss. However, some studies have found that LDL is reduced even without weight change, usually from burning at least 1,200 calories per week. While exercise may not consistently decrease LDLs, it may improve their quality. Early research suggests that regular aerobic exercise can produce more of the bigger, fluffier variety.

It’s unclear whether weight training affects cholesterol levels. Since changes seem dependent on total calories burned and weight training tends to burn fewer calories than moderate or vigorous aerobic activity, the impact appears minimal. Also, the jury is still out on whether intensity—how hard a workout is—plays a role. To see most cholesterol changes, exercise must be at least moderate (a brisk walk or cycle ride where you move at an intensity that feels “somewhat hard” or “hard.”. An exact dose-to-response has not been yet been determined, but a session may need to last long enough to burn around 350 calories at a time, or result in an accumulation of 1,200 to 2,500 calories over a week.

Exercise as an anti-cholesterol treatment does not work for everyone. Some people seem more resistant to changes, especially in HDLs, probably due to genetics. Keep in mind that using exercise is a slow approach and you may not see changes for three to six months, if you do at all. But even if exercise does not improve the numbers, exercise is always a good thing since it helps reduce other heart disease risk factors, such as high-blood pressure.

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Martica is a Manhattan-based exercise physiologist and nutritionist and an award-winning fitness instructor. She has written for a variety of publications including Self , Health , Prevention , The New York Times and others. Martica is the author of seven books, including her latest, - Cross-Training for Dummies . (Read her full bio.)