In atherosclerosis, cholesterol builds up in arteries, gradually narrowing them and restricting blood flow. Atherosclerosis is often caused by a diet high in saturated fat, trans fats, or dietary cholesterol (found in meat, eggs, and other foods). This can cause a rise in low-density lipoprotein (LDL)—also known as “bad cholesterol”—in the blood. In the first step toward atherosclerosis, LDL cholesterol penetrates the walls of arteries. Over time, the LDL cholesterol combines with calcium and other substances to form a fatty lump (known as a plaque) inside the artery. View a slideshow of the atherosclerosis process.

As the plaque gets larger, it starts to restrict blood flow. Atherosclerosis can cause leg pain and erectile dysfunction (depending on the plaque's location). But atherosclerosis is most dangerous when it occurs in the arteries that supply blood to the heart and brain, resulting in heart attacks and strokes.