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Encyclopedia > Food energy

Food energy is the amount of energy in food that is available through digestion. The values for food energy are expressed in kilocalories (kcal) and kilojoules (kJ). For the industrial process, see anaerobic digestion. ...


One food Calorie (1 kcal or 1,000 calories) 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 convention is not generally followed. The large Calorie is sometimes abbreviated kcal, to indicate clearly that is 1000 times as large as the small calorie formerly common in chemistry and physics usage. 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 the large calorie is less often used by laypersons. Etymology: French calorie, from Latin calor (heat), from calere (to be warm). ...


The International System of Units unit kilojoule (kJ) is becoming more common and is the unit officially recommended by the World Health Organization and other international organizations.[1] In some countries (Australia, for example) only the kilojoule is normally used. Some types of food contain more food energy per gram than others: fats and ethanol have particularly high values for food energy density: 9 and 7 kcal/g, respectively. Sugars and proteins have about 4 kcal/g. One (small) calorie is approximately equal to 4.1868 joules. One kcal is 4.1868 kJ. Look up si, Si, SI in Wiktionary, the free dictionary. ... A kilojoule (abbreviation: kJ) is a unit of energy equal to 1000 joules. ... WHO redirects here. ... For other uses, see FAT. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. ... Grain alcohol redirects here. ... Energy density is the amount of energy stored in a given system or region of space per unit volume, or per unit mass, depending on the context. ... Proteins are broken down in the stomach during digestion by enzymes known as proteases into smaller polypeptides to provide amino acids for the organism, including the essential amino acids that the organism cannot biosynthesize itself. ... The joule (IPA: or ) (symbol: J) is the SI unit of energy. ...


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.

Contents

Measuring food energy

The following process details how to measure food energy, as specified by the United States Department of Agriculture (USDA) in the early 1900s:


The particular food being measured must be burned in a calorimeter, so that the heat released from the food can be accurately measured. This amount is used to ascertain the G.E.V. of the specified food. This number is then multiplied by, usually, 85%; which is based on how the human digestive system. A calorimeter is a device used for calorimetry, the science of measuring the heat of chemical reactions or physical changes as well as heat capacity. ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature. ...


Food labels

The nutritional information label on a pack of Basmati rice in the United Kingdom
The nutritional information label on a pack of Basmati rice in the United Kingdom

The "calorie" has become a common household term because dietitians 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.[2] 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"[3], often as a substitute for the name of the quantity being measured, food energy; 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. Image File history File links Download high resolution version (629x1200, 157 KB) Summary Nutritional information label on a pack of Basmati rice (United Kingdom) Licensing I, the creator of this work, hereby release it into the public domain. ... Image File history File links Download high resolution version (629x1200, 157 KB) Summary Nutritional information label on a pack of Basmati rice (United Kingdom) Licensing I, the creator of this work, hereby release it into the public domain. ... Basmati rice, (basmati apparently means Queen of fragrance in the Hindi language) is a small long-grained variety of rice, famous for its fragrance and delicate flavour. ... A dietitian (sometimes spelled dietician) is an expert in food and nutrition. ... EU redirects here. ...


The amount of food energy in a particular food could be measured by completely burning the dried food in a bomb calorimeter, a method known as direct calorimetry.[4] However, the values given on food labels are not determined this way, because it overestimates the amount of energy that the human digestive system can extract, by also burning dietary fiber. Moreover, not all food energy eaten is actually resorbed by the body (fecal and urinal losses). Instead, standardized chemical tests or an analysis of the recipe using reference tables for common ingredients[5] 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:[6] A calorimeter is a device used for calorimetry, the science of measuring the heat of chemical reactions or physical changes as well as heat capacity. ... The world’s first ice-calorimeter, used in the winter of 1782-83, by Antoine Lavoisier and Pierre-Simon Laplace, to determine the heat evolved in various chemical changes; calculations which were based on Joseph Black’s prior discovery of latent heat. ... Dietary fibers are the indigestible portion of plant foods that move food through the digestive system, absorbing water and making defecation easier. ... A representation of the 3D structure of myoglobin showing coloured alpha helices. ... Lactose is a disaccharide found in milk. ... For other uses, see FAT. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. ...

food component energy density
kcal/g kJ/g
fat 9 37
ethanol (alcohol) 7 29
proteins 4 17
carbohydrates 4 17
organic acids 3 13
polyols (sugar alcohols, sweeteners) 2.4 10

Other substances found in food (water, non-digestible fibre, minerals, vitamins) do not contribute to this calculated energy density. For other uses, see FAT. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. ... Grain alcohol redirects here. ... A representation of the 3D structure of myoglobin showing coloured alpha helices. ... Lactose is a disaccharide found in milk. ... An organic acid is an organic compound that is an acid. ... The name polyols refers to chemical compounds containing multiple hydroxyl groups. ... A sugar alcohol (also known as a polyol, polyhydric alcohol, or polyalcohol) is a hydrogenated form of carbohydrate, whose carbonyl group (aldehyde or ketone, reducing sugar) has been reduced to a primary or secondary hydroxyl group. ...


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 [7] for conversions). Children, sedentary and older people require less energy, physically active people more. Look up day in Wiktionary, the free dictionary. ...


Energy usage in the human body

Energy intake to the body that is not used up is mostly stored as fat in the fat tissue. Consider the following theoretical calculation: 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. However, this calculation is somewhat theoretical, as the exact increase in fat tissue also depends on the form of energy intake. For example, food consisting mainly of fat can be converted into fat tissue quite efficiently, whereas carbohydrates cannot.[citation needed] Adipose tissue is an anatomical term for loose connective tissue composed of adipocytes. ...


Similarly, the exact conversion efficiency of food energy into physical power also depends on the exact form of energy source (type of food) and on the type of physical energy usage (e.g. which muscles are used, whether the muscle is used aerobically or anaerobically). In general, the efficiency of muscles is rather low, and roughly speaking, only about 15% of the food energy is actually converted into mechanical energy. For example, gym equipment manufacturers multiply the value of physical power (e.g. 150 watts on an exercise bike) by a factor of 8 when converting into "calories" (by which they mean large calories of food energy, e.g. 17 kcal/min which is 150 W × 8 = 1200 W). This is rather good news for food energy–aware sportsmen, as they can eat 8 times as much food energy as they have to work out in the gym. In physics, power (symbol: P) is the rate at which work is performed or energy is transmitted, or the amount of energy required or expended for a given unit of time. ... Aerobic exercise refers to exercise that is of moderate intensity, undertaken for a long duration. ... Fox and Haskell formula Anaerobic exercise is typically used by athletes in non-endurance sports to build power and by body builders to build muscle mass. ... For other uses, see Watt (disambiguation). ...


See also

In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... Basal metabolic rate (BMR) is the amount of energy expended while at rest in a neutrally temperate environment, in the post-absorptive state (meaning that the digestive system is inactive, which requires about twelve hours of fasting in humans). ... Food chains, food webs and/or food networks describe the feeding relationships between species to another within an ecosystem. ... The Atwater system (after Wilbur Olin Atwater) or derivatives of this system are used for the calculation of the available energy of foods. ... The nutrition facts label (also known as the nutrition information panel, and various other slight variations) is a label required on most pre-packaged foods in North America, United Kingdom and other countries. ...

References

  1. ^ The adoption of joules as units of energy, FAO/WHO Ad Hoc Committee of Experts on Energy and Protein, 1971.
  2. ^ European Union regulations on nutrition labeling
  3. ^ United States federal food-labeling regulations 21CFR101.9
  4. ^ Calories: Overview of Nutrition: Merck Manual Home Edition
  5. ^ Nutrient Value of Some Common Foods. Health Canada, PDF p. 4 (1997). Retrieved on 2006-03-04.
  6. ^ United Kingdom Food Labelling Regulations 1996 – Schedule 7: Nutrition labelling
  7. ^ EIA Energy Kids Page

PDF is an abbreviation with several meanings: Portable Document Format Post-doctoral fellowship Probability density function There also is an electronic design automation company named PDF Solutions. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 63rd day of the year (64th in leap years) in the Gregorian calendar. ...

External links


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