Since the 1970s, cholesterol has been closely associated with increased risk of developing heart disease. Although it has several vital functions in the body, over-consumption through the diet increases the likelihood of heart disease. Cholesterol is produced in the body, primarily in the liver. However, consuming animal tissue, which contains cholesterol, reduces the body's need to manufacture in the cells. Despite its vital roles in cell membrane structuring and the manufacturing of several hormones, cholesterol intake is recommended at less than 300mg, due to its association with heart disease. Aerobic exercise, in concert with a proper diet, is a suggested modality for the reduction of the risk for heart disease in cases of those individuals who suffer from hypercholesterolemia.
Cholesterol is transported through the body's bloodstream by spherical particles known as lipoproteins. Of the four types of lipoproteins, there are two that are of main concern for their involvement in heart disease. They are low-density lipoproteins (LDL) and high-density lipoproteins (HDL). LDLs are responsible for the transport of manufactured or ingested cholesterol throughout the body to carry out the aforementioned tasks of structural support and development of hormones. It is the duty of the HDLs to carry cholesterol to the liver for elimination. The problem that exists is when there is an overabundance of cholesterol, LDLs simply deposits it in and around arteries, causing buildup of fatty plaques. A typical high-fat, high-cholesterol diet produces much more cholesterol in the body than the HDLs can transport.
Research shows that moderate aerobic exercise increases the number of HDLs in the bloodstream and reduces the number of LDLs. Moderate aerobic exercise increases the need for lipid metabolism. Like fat, cholesterol is a lipid that can be oxidized, or broken down, for energy. Aerobic exercise must be maintained at moderate intensity levels in order for the body to rely on lipids for energy. High-intensity bouts of exercise become anaerobic (without oxygen) and precipitate the utilization of glucose for energy. Intensity dictates duration in exercise, and the longer the endurance, the more the body relies on lipid metabolism. Adherence to the recommended 5 days per week of physical activity lasting for 40 to 60 minutes, and maintaining moderate intensities, increases the number of HDLs, lowers the amount of LDLs in the body, and reduces the risks of heart disease.
References
- NSCA's Essentials of Personal Training, Earle, Roger and Baechle, Thomas. 2004
- Sports and Fitness Nutrition, Wildman, Robert and Miller, Barry
