Everything that the body does, from staying warm, to moving and thinking needs energy. The energy that we use comes from the proteins, carbohydrates and fats in our food. We are unable to use these directly, but instead need to convert them in to a form of energy that cells can use called ATP. You can think of this like a battery. This converts chemical energy into a different form (in this case electrical) that is easier to use. For our bodies the conversion from food energy to ATP happens in mitochondria. If your mitochondria are not working properly then you are less able to convert food into ATP. For cells that require a lot of ATP, for example your muscles, this is a problem and they may become weaker and get tired faster. Click the items below to learn more.