In scientific terms, a calorie is the quantity of heat required to raise the temperature of 1 gram of water 1 degree Celsius from a standard initial temperature. A nutritionist's calorie is defined as a unit of energy-producing potential equal to this quantity of heat that is contained in food and released upon oxidation by the body.
Food manufacturers are required to label their products with calorie guides. Calories of various products are determined through direct Calorimetry--that is, the measurement of the amount of head evolved or absorbed in a chemical reaction or change of state.
Energy-producing food is digested in the stomach and small intestines and eventually allows the body to build up muscle proteins, cleanse itself, strengthen bones and stabilize itself. Resting metabolic processes as well as growth mechanisms require energy, thus consume calories.
Those persons committed to maintaining proper weight often perform calorie counting. While most people require a daily calorie intake of 1,000 to 4,000 calories, depending on exercise, gender, lifestyle and age, the average person's caloric diet ranges from 1,500 to 2,400. Ingesting high calorie foods without adequately exercising results in calorie storage tantamount to fat storage.