Information about 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).
One 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 International System of Units unit kilojoule is becoming more common. 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/gram, respectively. Sugars and proteins have about 4 kcal/gram. One Calorie is approximately equal to 4.1868 joules.
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.
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.
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. 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 kilocalories); 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 bomb calorimeter, a method known as direct calorimetry.[1] 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 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 [3] for conversions). Children, sedentary and older people require less energy, physically active people more.
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 Watt on an exercise bike) by a factor of 8 when converting into "calories" (by which they mean kcal of food energy, e.g. 17 kcal/min which is 150W * 8 = 1200 W). This is rather good news for food energy aware sportsmen, as they can eat 8 times as many calories as they have to work out in the gym.
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One 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 International System of Units unit kilojoule is becoming more common. 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/gram, respectively. Sugars and proteins have about 4 kcal/gram. One Calorie is approximately equal to 4.1868 joules.
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
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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. 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 kilocalories); 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 bomb calorimeter, a method known as direct calorimetry.[1] 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 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:
| food component | energy density[2] | |
|---|---|---|
| kcal/g | kJ/g | |
| fat | 9 | 37 |
| ethanol (alcohol) | 7 | 29 |
| proteins | 4 | 17 |
| carbohydrates | 4 | 17 |
| organic acids | 3 | 13 |
| 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.
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 [3] for conversions). Children, sedentary and older people require less energy, physically active people more.
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.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 Watt on an exercise bike) by a factor of 8 when converting into "calories" (by which they mean kcal of food energy, e.g. 17 kcal/min which is 150W * 8 = 1200 W). This is rather good news for food energy aware sportsmen, as they can eat 8 times as many calories as they have to work out in the gym.
See also
- Chemical energy
- Basal Metabolic Rate
- Food chain
- Screaming jelly babies experiment showing food energy.
- Atwater system
- Nutrition facts label
References
1. ^ [1]
2. ^ Nutrient Value of Some Common Foods. Health Canada, PDF p. 4 (1997). Retrieved on 2006-03-04.
3. ^ [2]
2. ^ Nutrient Value of Some Common Foods. Health Canada, PDF p. 4 (1997). Retrieved on 2006-03-04.
3. ^ [2]
External links
- http://www.fao.org/docrep/006/Y5022E/y5022e04.htm
- http://www.ajcn.org/cgi/content/full/79/5/899S?ijkey=f3919ec7617632925bb12e0ffb8deeb08a678686 Is a calorie a calorie?
energy (from the Greek ενεργός, energos, "active, working")[1] is a scalar physical quantity that is a property of objects and systems of objects which is conserved by nature.
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Digestion is the process of metabolism whereby a biological entity processes a substance in order to chemically and mechanically convert the substance for the body to use.
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Overview
Digestion occurs at the multicellular, cellular, and sub-cellular levels, usually in animals...... Click the link for more information.
A calorie is a unit of measurement for energy. Calorie is French and derives from the Latin calor (heat). In most fields, it has been replaced by the joule, the SI unit of energy.
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Si, si, or SI may refer to (all SI unless otherwise stated):
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In language:
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The joule (IPA: [dʒuːl] or [dʒaʊl]) (symbol: J) is the SI unit of energy.
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Fat
Fat may refer to:- Fat, a group of compounds that are generally soluble in organic solvents and largely insoluble in water
- Adipose tissue, an anatomical term for loose connective tissue composed of adipocytes
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Ethanol, also known as ethyl alcohol, drinking alcohol or grain alcohol, is a flammable, colorless, slightly toxic chemical compound, and is best known as the alcohol found in alcoholic beverages.
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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. In some cases it is obvious from context which quantity is most useful: for example, in rocketry, energy per unit mass is the most
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A calorie is a unit of measurement for energy. Calorie is French and derives from the Latin calor (heat). In most fields, it has been replaced by the joule, the SI unit of energy.
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United States Department of Agriculture
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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 word calorimeter is derived from the Latin word calor, meaning heat.
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Combustion or burning is a complex sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames.
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coefficient is a constant multiplicative factor of a certain object. For example, the coefficient in 9x2 is 9.
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A dietitian (sometimes spelled dietician) is an expert in food and nutrition. Dietitians help promote good health through proper eating. They also supervise the preparation and service of food, develop modified diets, participate in research, and educate individuals and
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Obesity
Classification & external resources
Silhouettes representing healthy, overweight, and obese.
ICD-10 E 66.
ICD-9 278
DiseasesDB 9099
MedlinePlus 003101
eMedicine med/1653
MeSH C23.888.144.699.
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Classification & external resources
Silhouettes representing healthy, overweight, and obese.
ICD-10 E 66.
ICD-9 278
DiseasesDB 9099
MedlinePlus 003101
eMedicine med/1653
MeSH C23.888.144.699.
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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 word calorimeter is derived from the Latin word calor, meaning heat.
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Calorimetry is the science of measuring the heat of chemical reactions or physical changes. Calorimetry involves the use of a calorimeter. The word calorimetry is derived from the Latin word calor, meaning heat.
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Dietary fibers are the indigestible portion of plant foods that move food through the digestive system, absorbing water and making defecation easier. Dietary fiber consists of non-starch polysaccharides such as cellulose and many other plant components such as dextrins, inulin,
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Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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Fat
Fat may refer to:- Fat, a group of compounds that are generally soluble in organic solvents and largely insoluble in water
- Adipose tissue, an anatomical term for loose connective tissue composed of adipocytes
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Fat
Fat may refer to:- Fat, a group of compounds that are generally soluble in organic solvents and largely insoluble in water
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Ethanol, also known as ethyl alcohol, drinking alcohol or grain alcohol, is a flammable, colorless, slightly toxic chemical compound, and is best known as the alcohol found in alcoholic beverages.
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Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids whose acidity is associated with their carboxyl group -COOH. Sulfonic acids, containing the group OSO3H, are relatively stronger acids.
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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.
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