Cholesterol flows through your blood. High levels of LDL cholesterol can form a buildup of plaque on the walls of your blood vessels. This blocks your blood vessels and prevents healthy blood circulation. It can affect your heart and increase your risk of heart problems or stroke. LDL cholesterol levels can increase due to risk factors such as smoking, high blood pressure, diabetes, or a high-fat diet. Your body contains fats known as triglycerides. High triglycerides with high LDL and low HDL cholesterol levels can increase the chances of plaque buildup in your blood vessels.