There are two ways of getting energy for daily function, one is burning the nutrients from food, the carbohydrates and sugars especially. The other is burning stored fats. When we are eating, we derive energy to serve our muscular functions from the nutrients in the food. Extra nutrients are changed into fats which can be quickly oxidised or burned to supply energy if needed. When we fast or do not eat, if the body needs the energy to function, the reserves of fat are called up to be oxidised and provide energy for activities of the body that calls for it. After a meal, fat is stored. Between meals, stored fat is slowly released, keeping body cells supplied with energy. The brain needs the immediate, easily oxidised converted sugars (glucose) from food, the bodily organs burn the energy from stored fats. When we eat, nutrition not immediately burned is stored as fats. If we eat too much, we store excess fats until we have more stored fats than the body will reasonably use.