Food energy is the amount of energy in food that is available through digestion. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός Digestion is the breaking down of chemicals in the body into a form that can be absorbed The values for food energy are expressed in kilocalories (kcal) and kilojoules (kJ).

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. This article is about the unit of energy For its use in Nutrition and Food labelling regulations, see the article on Food energy. 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.

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. The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity ^[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. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water 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 although Sugars and proteins have about 4 kcal/g. Proteins are broken down in the Stomach during Digestion by Enzymes known as Proteases into smaller Polypeptides to provide One (small) calorie is approximately equal to 4. 1868 joules. The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity One kcal is 4. 1868 kJ.

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

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. A calorimeter is a device used for Calorimetry, the Science of measuring the heat of Chemical reactions or Physical changes as well as Heat In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature This amount is used to ascertain the G. E. V. of the specified food. This number is then multiplied by, usually, 85%; which represents the loss happening during human digestion.

Food labels

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. Basmati (बासमती باسمتی is a variety of long grain Rice, famous for its Fragrance and delicate flavour. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located A dietitian (also 'dietician' though 'dietitian' is used consistently by professionals is an expert in Food and Nutrition. Obesity is a condition in which excess Body fat has accumulated to such an extent that health may be negatively affected 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"). The European Union ( EU) is a political and economic union of twenty-seven member states, located primarily in 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 United States of America —commonly referred to as the 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. A calorimeter is a device used for Calorimetry, the Science of measuring the heat of Chemical reactions or Physical changes as well as Heat Calorimetry is the Science of measuring the Heat of Chemical ^[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. Dietary fibers are the indigestible portion of plant foods that move food through the Digestive system, absorbing water and easing Defecation. 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. Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Carbohydrates (from ' Hydrates of Carbon ' or saccharides ( Greek σάκχαρον meaning " Sugar " are the most Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water ). These results are then converted into an equivalent energy value based on a standardized table of energy densities:^[6]

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) for men and 2000 kcal/d (8 MJ/d) for women. A day (symbol d is a unit of Time equivalent to 24 Hours and the duration of a single Rotation of planet Earth with respect to the 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. "Adipose" redirects here For the Doctor Who monster see " Partners in Crime " Consider the following theoretical calculation.

• Fat contains about 3,500 kilocalories per pound (32 MJ/kg).
  • If you eat 3,500 kcal more than your body needs, you will put on about a pound of fat.
  • If you burn 3,500 kcal more than you eat, you will lose about a 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.

Similarly, the exact conversion efficiency of food energy into physical power also depends on the form of energy source (type of food) and on the type of physical energy usage (e. 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 g. which muscles are used, whether the muscle is used aerobically or anaerobically). Aerobic exercise refers to Exercise that involves or improves oxygen consumption by the body Anaerobic exercise is exercise intense enough to trigger anaerobic metabolism. 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, when calculating food energy burnt per unit time gym equipment manufacturers multiply the value of physical power by a factor of eight (assuming 12. 5% efficiency). Thus if an exercise bike registers a 150-watt physical power output it might display 17 kcal/min as the rate of food energy burnt per unit time (since 150 W × 8 = 1200 W ≈ 17 kcal/min).

See also

• Chemical energy
• Basal metabolic rate
• Food chain
• Atwater system
• Nutrition facts label

References

1. ^ The adoption of joules as units of energy, FAO/WHO Ad Hoc Committee of Experts on Energy and Protein, 1971. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός 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 Food chains, also called food networks and/or trophic networks, describe the feeding relationships between species within an Ecosystem. Entire article ref The Atwater system (after Wilbur Olin Atwater) or derivatives of this system are used for the calculation of the available energy 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
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. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 51 - Nero, later to become Roman Emperor, is given the title Princeps iuventutis (head of the youth
6. ^ United Kingdom Food Labelling Regulations 1996 – Schedule 7: Nutrition labelling

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?
• Calculate How Many Calories You Burn
• Calculate Calories To Maintain Body Weight