Energy is found in all living organisms across the world.
Different amounts of energy dwell in different beings. Less energy exists in animals than humans, and even less in plants. Trace amounts of energy are found in things considered (by non-magic users) to be inanimate, such as minerals and electricity.
For humans and anomalous humans, food and water is converted to energy. You might ask, "does food contain energy?" The answer to that is no. Inanimate objects, like food, do not contain energy. A body converts the food into energy by eating and digesting.
Converting energy by eating food doesn't reap as much energy as other sources such as physical and emotional absorption, blood, flesh, and souls. Demons are the most energy-hungry of all anomalies, and rely on energy-rich sustenance to avoid death.
The rawer the form of energy, the more potent. For example, demons prefer to feed on blood because it is very energy-rich. The most energy-rich part of the body is the soul. For more information on souls, please visit: Souls and Eyes.