A typical cheeseburger contains 17 grams of saturated fat and 86 milligrams of cholesterol. Eat this kind of food on a regular basis and, depending on your genetic makeup, a chain of events may begin, resulting in elevated blood cholesterol. 2. THE INTESTINES

Fat and cholesterol are packaged as lipoproteins and sent throughout the body via the blood system. Muscle and fat cells extract what they need for energy, and the remnants continue on to the liver. 3. THE LIVER

The fat and cholesterol remnants are absorbed from the blood. Then the liver sends out more fat-cholesterol packets (in the form of VLDL, very-low-density lipoproteins) for use by the body. The excess is reabsorbed again. Through this constant reprocessing, an equilibrium is maintained, and blood cholesterol remains at safe levels.

Sometimes, the reprocessing system fails. In some people, there is a genetic shortage of special fat receptors on liver cells, preventing the recycling of the fat-cholesterol packets. In others, a high-fat diet overtaxes the liver's ability to process the packets. In either case, the result is the same: there is a buildup of a dangerous form of lipoprotein in the blood -- low-density lipoproteins, or LDL. 4. THE ARTERIES

LDL is sticky; it attaches to any imperfection or nick in the blood vessel wall. Soon, it is joined by other body cells, forming a plaque. This narrows blood vessels, increases blood pressure and can cause a heart attack or stroke. 5. THE GOOD CHOLESTEROL

Part of this complex reprocessing system involves the production of high-density lipoproteins, or HDL, produced in various parts of the body. This form of fat-cholesterol packet acts as a cleansing agent, removing excess cholesterol from the blood.