heat equivalence

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The energy released by the combustion of food in 1 litre of oxygen. The heat equivalence of a particular food varies according to its proportions of carbohydrate, fat, and protein. One litre of oxygen releases 5.0 kilocalories of energy from carbohydrates; 4.7 kilocalories from fats; and 4.5 kilocalories from protein. Thus, carbohydrates provide the most energy per litre of oxygen. In addition, for a given level of energy expenditure, more oxygen has to be inhaled if fat, rather than carbohydrate, is used as an energy source. See also metabolic equivalent.

Energy produced by the oxidation of food using 1 litre of oxygen. Heat equivalence varies according to the mixture of food types (fats, carbohydrate, or protein) being oxidized. It is usually measured in kilo-calories. See also net oxygen cost of exercise, respiratory quotient.