How Do People Get Energy?
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Food Contains Energy Sources
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Virtually every item that exists, whether it can be ingested or not, contains some amount of stored energy. In foods, a complex mathematical calculation is used to derive the energy content of the food item; in a process known as "Factorial Method," the energy provided by each component of the food item -- components like fat, carbs, and proteins -- is analyzed, calculated, and added together to provide the entire energy value of the item. This process is still somewhat challenging, however, as not all portions of the food item can be digested; in addition, different types of carbohydrates provide varying amounts of energy. Regardless of the exact energy content, however, the food item does offer at least some energy to the person who consumes it.
People Digest Food
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When food items are eaten, they are broken down to a molecular level by the person's digestive system. Once it has been broken all the way down into microscopic molecules, the food can be circulated to the various systems of the body. Energy is absorbed from the food throughout the entire digestive process, though the bulk of carbohydrate energy, the prevalent source of energy in most Western food, is absorbed in the small intestine and distributed to the body. Of course, not all of the energy stored in the food item can be circulated or even absorbed by the body; some is simply too complex to be digested while part of the energy is burned during the digestive process (still other energy is released in the form of body heat).
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The Body Stores Some Energy
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As the food is absorbed by the body, it is circulated to cells, where it is either immediately used or stored as energy. Some of the energy from the food is burned during the distribution process, while a portion of it is delivered and immediately used by the receiving cell (this immediate use is the reason why carbohydrate-rich food sources seem to produce a sudden burst of energy shortly after consumption). In many cases, not all of the item's energy can be put to immediate use; to allow for the most efficient retention, the body stores this excess energy in fat cells. When the body begins to run low on energy, as happens when too few calories are consumed or in periods of heavy exercise, the body converts the fat cells back into usable energy for instant use.
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