Triglycerides (or triacylglycerols), one of the three classes of fats are glycerides in which one molecule of glycerol is esterified with three fatty acids. Triglycerides are one of three major sources of metabolic fuel (the other sources are carbohydrates and proteins) providing energy for the physiological processes of the body. They are the main constituent of vegetable oil and animal fats and part of all blood lipids, where they circulate bound to protein, forming high- and low-density lipoproteins, especially, the low-density types. Fat in the body is stored as triglycerides and blood levels are useful in diagnosing and treating diabetes, high blood pressure, and heart disease. A high level of blood triglycerides, known as hypertriglyceridemia, is associated with atherosclerosis, both of which in turn can be complications of diabetes. In the liver, fatty acids are incorporated into triglycerides and secreted as VLDL; in the intestines, fatty acids are incorporated into triglycerides and secreted as chylomicrons. High levels of triglycerides are usually indicative of high levels of insulin. The ratio of TG/HDL is a powerful indicator of insulin levels and is strongly predictive of future cardiovascular events. High levels of triglycerides may accompany poorly controlled diabetes and may play a role in the development of heart disease. Some triglycerides circulate in the blood to provide fuel for muscles to work. Extra triglycerides are found in the blood after eating a meal when fat is being sent from the gut to adipose tissue for storage. Most triglycerides are obtained from food as fats or synthesized by the liver and stored in liver and fat cells (adipocytes).