Too much cholesterol and other fats can lead to disease, and that a healthy diet involves watching how much fatty food we eat. However, our bodies need a certain amount of fat to function—and we can't make it from scratch.
Triglycerides, cholesterol and other essential fatty acids—the scientific term for fats the body can't make on its own—store energy, insulate us and protect our vital organs. They act as messengers, helping proteins do their jobs. They also start chemical reactions that help control growth, immune function, reproduction and other aspects of basic metabolism.
The cycle of making, breaking, storing and mobilizing fats is at the core of how humans and all animals regulate their energy. An imbalance in any step can result in disease, including heart disease and diabetes. For instance, having too many triglycerides in our bloodstream raises our risk of clogged arteries, which can lead to heart attack and stroke.
Fats help the body stockpile certain nutrients as well. The so-called "fat-soluble" vitamins—A, D, E and K—are stored in the liver and in fatty tissues.