A unit of energy. Two units are called by this name. The small calorie, or gram calorie, is the amount of heat required to raise one gram of water one degree centigrade in temperature.
The large Calorie or kilocalorie, which is used in the study of dietetics and physiological processes, is the amount of heat required to raise one kilogram of water one degree centigrade in temperature. The number of Calories required to carry on the processes necessary for life and body warmth – such as the beating of the heart, the movements of the chest in breathing, and the chemical activities of the secreting glands – is, for an adult person of ordinary weight, somewhere in the neighbourhood of 1,600. For ordinary sedentary occupations an individual requires about 2,500 Calories; for light muscular work slightly over 3,000 Calories; and for hard continuous labour around 4,000 Calories daily.
Under the International System of Units (SI UNITS – see APPENDIX 6: MEASUREMENTS IN MEDICINE) the kilocalorie has been replaced by the joule, the abbreviation for which is J (1 kilocalorie=4,186·8 J). The term Calorie, however, is so well established that it has been retained in this edition. Conversion from Calories (or kilocalories) to joules is made by multiplying by 4·2 .... calorie
The amount of energy that is needed by a person for cell metabolism, muscular activity, and growth. This energy is provided by the breakdown of carbohydrates, fats, and proteins supplied by food in the diet and by stored nutrients in the liver, muscles, and adipose tissue.
Energy is needed to maintain the heartbeat, lung function, and constant body temperature. The rate at which these processes use energy is called the basal metabolic rate (BMR). Any form of movement increases energy expenditure above the BMR. A person’s energy requirement increases during periods of growth and during pregnancy and lactation. When more energy is ingested as food than is used, the surplus is stored and there is usually a gain in weight. When less energy is consumed than is spent, weight is usually lost as the stores are used up. (See also nutrition; obesity.)... energy requirements
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