Every living thing has a way of taking raw materials from its environment, turning those materials into energy, and disposing of the waste products it no longer needs. While this process is not the only definition of the word metabolism, it is this digestive process that most people think of when you use the word. Although not every organism uses the same process to create energy (plants use photosynthesis, for example), humans all have to eat food in order to gain energy. The way your body uses that energy is often called a metabolism.