Despite its bad reputation, cholesterol plays a very important role in healthy anatomy and physiology. Cholesterol is a waxy compound found in your bloodstream and in all the cells of your body, where it keeps cell membranes flexible. Additionally, cholesterol is an essential building block for several hormones. Cholesterol is carried through the body mainly by two types of lipoprotein transporters -- LDL and HDL. Research to-date indicates that moderate to strenuous exercise tends to significantly increase HDL levels and may help to decrease LDL levels.
Cholesterol
Cholesterol levels are regulated internally by the body -- if you aren't consuming enough cholesterol from dietary sources, the body will make more to compensate. However, it is possible to eat so much saturated or trans fats that you overload the regulatory system and cholesterol begins to accumulate to unhealthy levels. This condition is called hypercholesterolemia -- a definitive risk factor for heart disease. Regular exercise seems to help keep cholesterol levels within a healthy range.
Lipoproteins
Cholesterol is insoluble in the blood and transported about the body by carriers called lipoproteins. High-density lipoproteins appear to be responsible for transporting cholesterol away from the peripheral vasculature and back to the liver, where the cholesterol is destroyed. HDL is called the "good" cholesterol because high levels of this lipoprotein are associated with heart health. Conversely, low-density lipoproteins carry cholesterol through the systemic circulation. If LDL levels become too high, cholesterol is deposited along the walls of arteries, forming plaque. The hardened plaque causes blood clots to form and may lead to a heart attack or stroke.
Exercise
Researchers have found it is far easier to boost levels of "good" cholesterol than it is to reduce the amount of "bad" cholesterol in your system. For instance, regular and vigorous exercise appears to increase the body's production of HDL significantly. For exercise to have an effect on HDL levels, however, you must exercise at least 30 minutes a day, 6 days per week with moderate or intense energy expenditure. The effect of exercise on LDL levels is less clear. Some significant reductions in LDL levels have been seen, but generally only in individuals who are losing weight and body fat at the same time.
LDL
Although the jury is still out on whether exercise significantly reduces LDL levels, it is very unlikely that regular moderate or strenuous exercise will increase your "bad" cholesterol. All indications of current research are that, at the very least, fitness increases "good" cholesterol and that in itself may quite possibly help to reduce your LDL. The benefits of regular exercise on your overall cardiovascular health are also quite significant. If you have high cholesterol, speak with your physician about devising a plan to decrease your LDL levels and increase HDL levels by combining a healthy diet with regular exercise.
