What Do Fats Do in the Body?

It's common knowledge that 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...