The process of energy expenditure and the oxidation or combustion of food for energy in the body is analogous to a woodburning stove, which burns wood to release heat in a controlled fashion. In the wood stove analogy, large chunks of wood are fed to the stove, and the wood is gradually combusted in the presence of oxygen to release carbon dioxide, water vapor, and heat. This process is similar to what happens in the body when food is consumed: Food is consumed by the body and is oxidized or combusted in the presence of oxygen to release carbon dioxide, water, and heat. When ingested food is used for energy, how- ever, the release and transfer of energy occurs through a series of tightly regulated metabolic pathways, in which the potential energy from food is released slowly and gradually over time. This process ensures that the body is provided with a gradual and constant energy store, rather than relying on a sudden release of energy from an immediate combus- tion of ingested food. As a simple example of how the body uses food for energy, consider the combustion of a simple glucose molecule as follows: