What Is Atherosclerosis? Atherosclerosis is a condition where plaque (a mixture of fat, cholesterol, and other substances) builds up inside your arteries, making them narrower and harder. This reduces the amount of oxygen-rich blood flowing to vital organs and can lead to serious health problems like heart attacks, strokes, and even organ damage. Early detection is key, but prevention through a balanced diet, exercise, and managing risk factors like high cholesterol is the best defense against a