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One large food Calorie is the amount of digestively available food energy (heat) that will raise the temperature of one kilogram of water one degree Celsius. Some advocate the convention of the capitalizing the ''C'' in these so that one Calorie is equal to 1000 lowercase calories, but that is not a convention generally followed. The large Calorie is sometimes abbreviated kcal, to indicate clearly that is 1000 times as large as the calorie. Consequently, the prefix kilo- is not used with large Calories. Food calories are also more specifically called ''kilocalories'' on the basis of the small calorie usage. This term, which makes it clear that large Calories are intended, is widely used by professional nutritionists when speaking in terms of calories rather than joules, but the term ''kilocalorie'' for 1,000 small calories is less often used by laypersons. The is approximately equal to 4.1868 kilojoules. Each food item has a specific metabolizable energy intake (MEI). For a normal human this value is obtained by multiplying the number of kilocalories or kilojoules contained in a food item by 85%, which is the amount of energy actually obtained by a human after the digestive processes have been completed. MEASURING FOOD ENERGY In the early twentieth century, the United States Department of Agriculture ( USDA ) developed a procedure for measuring food energy that remains in use today. The food being measured is completely burned in a Calorimeter so that the Heat released through Combustion can be accurately measured. This amount is used to determine the gross energy value of the particular food. This number is then multiplied by a Coefficient which is based on how the human body actually digests the food. NUTRITION AND FOOD LABELS in the United Kingdom ]] The "Calorie" has become a common household term, because Dietitian s recommend in cases of Obesity to reduce body weight by increasing exercise (energy expenditure) and reducing energy intake. Many governments require food manufacturers to label the energy content of their products, to help consumers control their energy intake. In Europe , manufacturers of prepackaged food must label the nutritional energy of their products in both kilocalories ("kcal") and kilojoules ("kJ"). In the United States , the equivalent mandatory labels display only "Calories" (when used with ''capitalized'' C, meaning ''kilo''calories); an additional kilojoules figure is optional and is rarely used. The energy content of food is usually given on labels for 100 g and/ or for what the manufacturer claims is a typical serving size. The amount of food energy in a particular food could be measured by completely burning the dried food in a . Instead, standardized chemical tests and an analysis of the recipe are used to estimate the product's digestible constituents ( Protein , Carbohydrate , Fat , etc.). These results are then converted into an equivalent energy value based on a standardized table of energy densities: Other substances found in food (water, non-digestible fibre, minerals, vitamins) do not contribute to this calculated energy density. Recommended daily energy intake values for young adults are: 2500 kcal/ D (10 MJ/d, 2.8 kWh) for men and 2000 kcal/d (8 MJ/d, 2.3 kWh) for women (cf http://www.eia.doe.gov/kids/energyfacts/science/energy_calculator.html for conversions). Children, sedentary and older people require less energy, physically active people more. About 3,500 kcal are contained in 1 pound of fat. If you eat 3,500 kcal more than your body needs, you will put on about 1 pound of fat. If you burn 3,500 kcal more than you eat, you will lose about 1 pound of fat. This assumes that all the weight gained and lost is in the form of fat. In reality, muscle and organ mass will change as well. SEE ALSO
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