The calorie is a unit of energy. The Calorie (note the capital C) is 1,000 calories.

That capital C, distinguishing Calorie from calorie, is a long-established scientific convention but is not always understood more widely. Where the context is clearly about food, nutrition and exercise, the term often appears without the capital C.[1] The Calorie is also termed the large calorie or kilocalorie — symbols: Cal, kcal — or food calorie, defined as the heat energy involved in warming one kilogram of water by one degree Celsius.[2]

The small calorie (symbol: cal) was later defined as the heat energy to raise the temperature of one gram of water — rather than a kilogram — by the same amount. (See below for details of the definitions.)

Although both units relate to the metric system, they have been considered obsolete, or deprecated, in scientific usage, since the adoption of the SI system.[3] (The SI unit of energy is the joule.) But the small calorie is still often used in laboratory measurements and calculations, with the values thus established typically being reported in kilocalories.

Energy drink and fast food cheeseburger calorie comparison
A 710-millilitre (24 US fl oz) energy drink with 330 kcal, more than a fast-food cheeseburger, and the equivalent of 18 single-serving packets of sugar


The (large) calorie was first defined by Nicolas Clément in 1824 as a unit of heat energy.[3] It entered French and English dictionaries between 1841 and 1867. The word comes from Latin calor, meaning 'heat'. The small calorie was introduced by Pierre Antoine Favre (Chemist) and Johann T. Silbermann (Physicist) in 1852. In 1879, Marcellin Berthelot introduced the convention of capitalizing the large Calorie to distinguish the senses. The use of the (large) calorie for nutrition was introduced to the American public by Wilbur Olin Atwater, a professor at Wesleyan University, in 1887.[3]

The alternate spelling calory is archaic.


The energy needed to increase the temperature of a given mass of water by 1 °C depends on the atmospheric pressure and the starting temperature. Accordingly, several different precise definitions of the calorie have been used.

The pressure is usually taken to be the standard atmospheric pressure (101.325 kPa). The temperature increase can be expressed as one kelvin, which means the same as an increment of one degree Celsius.

Name Symbol Conversions Notes
Thermochemical calorie calth 4.184 J

≈ 0.003964 BTU ≈ 1.162×10−6 kWh ≈ 2.611×1019 eV

the amount of energy equal to exactly 4.184 joules [4][a][6][7]
4 °C calorie cal4 ≈ 4.204 J

≈ 0.003985 BTU ≈ 1.168×10−6 kWh ≈ 2.624×1019 eV

the amount of energy required to warm one gram of air-free water from 3.5 to 4.5 °C at standard atmospheric pressure.
15 °C calorie cal15 ≈ 4.1855 J

≈ 0.0039671 BTU ≈ 1.1626×10−6 kWh ≈ 2.6124×1019 eV

the amount of energy required to warm one gram of air-free water from 14.5 to 15.5 °C at standard atmospheric pressure. Experimental values of this calorie ranged from 4.1852 to 4.1858 J. The CIPM in 1950 published a mean experimental value of 4.1855 J, noting an uncertainty of 0.0005 J.[4]
20 °C calorie cal20 ≈ 4.182 J

≈ 0.003964 BTU ≈ 1.162×10−6 kWh ≈ 2.610×1019 eV

the amount of energy required to warm one gram of air-free water from 19.5 to 20.5 °C at standard atmospheric pressure.
Mean calorie calmean ≈ 4.190 J

≈ 0.003971 BTU ≈ 1.164×10−6 kWh ≈ 2.615×1019 eV

1100 of the amount of energy required to warm one gram of air-free water from 0 to 100 °C at standard atmospheric pressure.
International Steam table calorie (1929) ≈ 4.1868 J

≈ 0.0039683 BTU ≈ 1.1630×10−6 kWh ≈ 2.6132×1019 eV

1860 international watt hours = ​18043 international joules exactly.[note 1]
International Steam Table calorie (1956) calIT ≡ 4.1868 J

≈ 0.0039683 BTU = 1.1630×10−6 kWh ≈ 2.6132×1019 eV

1.163 mW·h = 4.1868 J exactly. This definition was adopted by the Fifth International Conference on Properties of Steam (London, July 1956).[4]
  1. ^ The figure depends on the conversion factor between international joules and absolute (modern) joules. Using the mean international ohm and volt (1.00049 Ω, 1.00034 V[8]), the international joule is about 1.00019 J, using the US international ohm and volt (1.000495 Ω, 1.000330 V) it is about 1.000165 J, giving 4.18684 and 4.18674 J, respectively.

The two definitions most common in older literature appear to be the 15 °C calorie and the thermochemical calorie. Until 1948, the latter was defined as 4.1833 international joules; the current standard of 4.184 J was chosen to have the new thermochemical calorie represent the same quantity of energy as before.[6]

The calorie was first defined specifically to measure energy in the form of heat, especially in experimental calorimetry.[9]


In a nutritional context, the kilojoule (kJ) is the SI unit of food energy, although the kilocalorie is still in common use.[10] The word calorie is popularly used with the number of kilocalories of nutritional energy measured. To avoid confusion, it is sometimes written Calorie (with a capital "C") to make the distinction, although this is not widely understood (in part because capitalization contravenes the SI rule that the initial letter of a unit name or its derivative shall be lower case in English).[11]

To facilitate comparison, specific energy or energy density figures are often quoted as "calories per serving" or "kilocalories per 100 g". A nutritional requirement or consumption is often expressed in calories per day. One gram of fat in food contains nine calories, while a gram of either a carbohydrate or a protein contains approximately four calories.[12] Alcohol in a food contains seven calories per gram.[13]


In other scientific contexts, the term calorie almost always refers to the small calorie. Even though it is not an SI unit, it is still used in chemistry. For example, the energy released in a chemical reaction per mole of reagent is occasionally expressed in kilocalories per mole.[14] Typically, this use was largely due to the ease with which it could be calculated in laboratory reactions, especially in aqueous solution: a volume of reagent dissolved in water forming a solution, with concentration expressed in moles per liter (1 liter weighing 1 kg), will induce a temperature change in degrees Celsius in the total volume of water solvent, and these quantities (volume, molar concentration and temperature change) can then be used to calculate energy per mole. It is also occasionally used to specify energy quantities that relate to reaction energy, such as enthalpy of formation and the size of activation barriers.[15] However, its use is being superseded by the SI unit, the joule, and multiples thereof such as the kilojoule.

Measurement of energy content of food

In the past a bomb calorimeter was utilised to determine the energy content of food by burning a sample and measuring a temperature change in the surrounding water. Today this method is not commonly used in the USA and has been succeeded by calculating the energy content indirectly from adding up the energy provided by energy-containing nutrients of food (such as protein, carbohydrates and fats). The fibre content is also subtracted to account for the fact fibre is not digested by the body.[12]

See also


  1. ^ "The 'Thermochemical calorie' was defined by Rossini simply as 4.1833 international joules in order to avoid the difficulties associated with uncertainties about the heat capacity of water (it has been redefined as 4.1840 J exactly)."[5]


  1. ^ Conn, Carole; Len Kravitz. "Remarkable Calorie". University of New Mexico. Retrieved 1 March 2019.
  2. ^ "Definition of Calorie". Merriam-Webster. August 1, 2017. Retrieved September 4, 2017.
  3. ^ a b c Hargrove, James L (2007). "Does the history of food energy units suggest a solution to "Calorie confusion"?". Nutrition Journal. 6 (44). doi:10.1186/1475-2891-6-44. PMC 2238749. PMID 18086303. Retrieved 31 August 2013.
  4. ^ a b c International Standard ISO 31-4: Quantities and units, Part 4: Heat. Annex B (informative): Other units given for information, especially regarding the conversion factor. International Organization for Standardization, 1992.
  5. ^ FAO (1971). "The adoption of joules as units of energy".
  6. ^ a b Rossini, Fredrick (1964). "Excursion in Chemical Thermodynamics, from the Past into the Future". Pure and Applied Chemistry. 8 (2): 107. doi:10.1351/pac196408020095. Retrieved 21 January 2013. both the IT calorie and the thermochemical calorie are completely independent of the heat capacity of water.
  7. ^ Lynch, Charles T. (1974). Handbook of Materials Science: General Properties, Volume 1. CRC Press. p. 438. Retrieved 8 March 2014.
  8. ^ International Union of Pure and Applied Chemistry (IUPAC) (1997). "1.6 Conversion tables for units". Compendium of Analytical Nomenclature (PDF) (3 ed.). ISBN 0-86542-615-5. Retrieved 31 August 2013.
  9. ^ Allain, Rhett (February 23, 2016). "Calculating Calories by Burning Gummy Bears to Death". Scientific American. Retrieved September 7, 2017.
  10. ^ "Prospects improve for food energy labelling using SI units". Metric Views. UK Metric Association. 24 February 2012. Retrieved 17 April 2013.
  11. ^ "SI Conventions". National Physical Laboratory. Retrieved 8 February 2016.
  12. ^ a b "How Do Food Manufacturers Calculate the Calorie Count of Packaged Foods?". Scientific American. Retrieved 2017-09-08.
  13. ^ "Calories - Fat, Protein, Carbohydrates, Alcohol. Calories per gram".
  14. ^ Zvi Rappoport ed. (2007), "The Chemistry of Peroxides", Volume 2 page 12.
  15. ^ Bhagavan, N. V. (2002). Medical Biochemistry. Academic Press. pp. 76–77. ISBN 9780120954407. Retrieved 5 September 2017.

A bombolone (pl. bomboloni) is an Italian filled doughnut (similar to the Berliner, krafne, etc.) and is eaten as a snack food and dessert. The pastry's name is etymologically related to bomba (bomb), and the same type of pastry is also called bomba (pl. "bombe") in some regions of Italy. The etymological connection is probably due to the resemblance to a grenade or old-fashioned bomb and may today possibly also be regarded as a reference to the very high calorie density of this recipe (i.e., a "calorie bomb").

British thermal unit

The British thermal unit (Btu or BTU) is a traditional unit of heat; it is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. It is also part of the United States customary units. Its counterpart in the metric system is the calorie, which is defined as the amount of heat required to raise the temperature of one gram of water by one degree Celsius. Heat is now known to be equivalent to energy, for which the SI unit is the joule; one BTU is about 1055 joules. While units of heat are often supplanted by energy units in scientific work, they are still used in many fields. As examples, in the United States the price of natural gas is quoted in dollars per million BTUs.

Calorie restriction

Calorie restriction, caloric restriction, or energy restriction, is a dietary regimen that reduces calorie intake without incurring malnutrition or a reduction in essential nutrients. "Reduce" can be defined relative to the subject's previous intake before intentionally restricting calories, or relative to an average person of similar body type. Commonly consumed food components containing calories are carbohydrates, proteins and fat.

In preliminary research, some non-human species on calorie restriction diets without malnutrition may exhibit slowing of the biological aging process, resulting in an increase in both median and maximum lifespan, but this effect is not universal. In humans, the long-term health effects of moderate caloric restriction with sufficient nutrients are unknown.


A calorimeter is an object used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal micro calorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber. It is one of the measurement devices used in the study of thermodynamics, chemistry, and biochemistry.

To find the enthalpy change per mole of a substance A in a reaction between two substances A and B, the substances are separately added to a calorimeter and the initial and final temperatures (before the reaction has started and after it has finished) are noted. Multiplying the temperature change by the mass and specific heat capacities of the substances gives a value for the energy given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction.

Where q is the amount of heat according to the change in temperature measured in joules and Cv is the heat capacity of the calorimeter which is a value associated with each individual apparatus in units of energy per temperature (Joules/Kelvin).


D'Lites of America was an American fast food chain based in Norcross, Georgia. It was known for serving fast food with a higher emphasis on nutrition. It featured reduced-calorie dishes, including hamburgers made with lean beef, high-fiber buns, and low-calorie cheese.It was founded in 1978 by Doug Sheley and Jeffrey Miller. The first franchises opened in 1983. By 1985, more than 100 stores were opened.The chain stopped franchising in 1986 and closed several stores. By year's end, it had filed for Chapter 11 bankruptcy. In 1987, ninety percent of the remaining company-owned stores were sold to Hardee's and were soon rebranded as Hardee's. A few D'Lites restaurants remain, but they are under new ownership and have been renamed to avoid infringement of the D'Lites name.According to FIU Hospitality Review, the chain's closure was due to other chains such as McDonald's, Burger King, and Wendy's beginning to offer healthier sides such as salads and baked potatoes, as well as D'Lites' buying back of several unsuccessful franchise locations.

Diet drink

Diet (alternatively marketed as sugar-free, zero-calorie or low-calorie) drinks are sugar-free, artificially sweetened versions of fizzy beverages with virtually no calories. They are generally marketed toward health-conscious people, diabetics, athletes, and other people who want to lose weight, improve physical fitness, or reduce their sugar intake. However, studies show that the marketed effectiveness of diet soft drinks is questionable.

Diet food

Diet food (or dietetic food) refers to any food or beverage whose recipe is altered to reduce fat, carbohydrates, abhor/adhore sugar in order to make it part of a weight loss program or diet. Such foods are usually intended to assist in weight loss or a change in body type, although bodybuilding supplements are designed to aid in gaining weight or muscle.


Dieting is the practice of eating food in a regulated and supervised fashion to decrease, maintain, or increase body weight, or to prevent and treat diseases, such as diabetes. A restricted diet is often used by those who are overweight or obese, sometimes in combination with physical exercise, to reduce body weight. Some people follow a diet to gain weight (usually in the form of muscle). Diets can also be used to maintain a stable body weight and improve health.

Diets to promote weight loss can be categorized as: low-fat, low-carbohydrate, low-calorie, very low calorie and more recently flexible dieting. A meta-analysis of six randomized controlled trials found no difference between low-calorie, low-carbohydrate, and low-fat diets, with a 2–4 kilogram weight loss over 12–18 months in all studies. At two years, all calorie-reduced diet types cause equal weight loss irrespective of the macronutrients emphasized. In general, the most effective diet is any which reduces calorie consumption.A study published in American Psychologist found that short-term dieting involving "severe restriction of calorie intake" does not lead to "sustained improvements in weight and health for the majority of individuals". Other studies have found that the average individual maintains some weight loss after dieting. Weight loss by dieting, while of benefit to those classified as unhealthy, may slightly increase the mortality rate for individuals who are otherwise healthy.The first popular diet was "Banting", named after William Banting. In his 1863 pamphlet, Letter on Corpulence, Addressed to the Public, he outlined the details of a particular low-carbohydrate, low-calorie diet that had led to his own dramatic weight loss.

Empty calories

In human nutrition, the term empty calories applies to foods and beverages composed primarily or solely of sugar, fats or oils, or alcohol-containing beverages. An example is carbonated soft drinks. These supply food energy but little or no other nutrition in the way of vitamins, minerals, protein, fiber, or essential fatty acids. Fat contributes nine calories per gram, ethanol seven calories, sugar four calories. The U.S. Department of Agriculture (USDA) advises, "A small amount of empty calories is okay, but most people eat far more than is healthy." The phrase is derived from low nutrient density, which is the proportion of nutrients in a food relative to its energy content.Considering energy foods as adequate nutrition was first scientifically demonstrated to be false by François Magendie by experiments on dogs and described in his Précis élémentaire de Physiologie. He showed that eating only sugar, olive oil, or butter, each led to the death of his test animals in 30 to 40 days.


Enviga is a Nestea carbonated canned green-tea drink. Enviga is a trademark of Nestlé licensed to Beverage Partners Worldwide, a joint-venture between The Coca-Cola Company and Nestlé. It is available in three flavors: Green Tea, Tropical Pomegranate, and Mixed Berry. According to Coca-Cola, Enviga burns 60 to 100 calories per three 12-oz.(330 ml) cans due to its high EGCG and caffeine content. This is disputed by some researchers and public advocates.

Essential amino acid

An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized de novo (from scratch) by the organism at a rate commensurate with its demand, and thus must be supplied in its diet. Of the 20 amino acids common to all life forms, the nine amino acids humans cannot synthesize are phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine.Six other amino acids are considered conditionally essential in the human diet, meaning their synthesis can be limited under special pathophysiological conditions, such as prematurity in the infant or individuals in severe catabolic distress. These six are arginine, cysteine, glycine, glutamine, proline, and tyrosine. Six amino acids are non-essential (dispensable) in humans, meaning they can be synthesized in sufficient quantities in the body. These six are alanine, aspartic acid, asparagine, glutamic acid, serine, and selenocysteine (considered the 21st amino acid). Pyrrolysine (considered the 22nd amino acid) is not used by humans; thus, it is non‑essential.

Food energy

Food energy is chemical energy that animals (including humans) derive from food through the process of cellular respiration. Cellular respiration may either involve the chemical reaction of food molecules with molecular oxygen (aerobic respiration) or the process of reorganizing the food molecules without additional oxygen (anaerobic respiration).

Intermittent fasting

Intermittent fasting (intermittent energy restriction or intermittent calorie restriction) is an umbrella term for various eating diet plans that cycle between a period of fasting and non-fasting over a defined period. Intermittent fasting is under preliminary research to assess if it can produce weight loss comparable to long-term calorie restriction.

List of diets

An individual's diet is the sum of food and drink that he or she habitually consumes. Dieting is the practice of attempting to achieve or maintain a certain weight through diet. People's dietary choices are often affected by a variety of factors, including ethical and religious beliefs, clinical need, or a desire to control weight.

Not all diets are considered healthy. Some people follow unhealthy diets through habit, rather than through a conscious choice to eat unhealthily. Terms applied to such eating habits include "junk food diet" and "Western diet". Many diets are considered by clinicians to pose significant health risks and minimal long-term benefit. This is particularly true of "crash" or "fad" diets–short-term, weight-loss plans that involve drastic changes to a person's normal eating habits.

Only diets covered on Wikipedia are listed.

Meal replacement

A meal replacement is a drink, bar, soup, etc. intended as a substitute for a solid food meal, usually with controlled quantities of calories and nutrients. Some drinks are in the form of a health shake. Medically prescribed meal replacement drinks include the required vitamins and minerals. Bodybuilders sometimes use meal replacements, not formulated for weight loss, to save food preparation time when they are eating 5 to 6 meals a day.In the European Union, weight-reduction meal replacements intended either to supplement ("Meal replacement for weight control") or to replace totally ("Total diet replacement for weight control") normal meals are regulated as to their energy content, the nutrients they must provide, and information and advice on packaging by COMMISSION DIRECTIVE 96/8/EC of 26 February 1996 on foods intended for use in energy-restricted diets for weight reduction. For example, a meal replacement must provide between 200 and 400 food calories of energy, of which not more than 30% from fat, and not less than specified amounts for various vitamins and minerals. Labeling information is prescribed, and packaging must provide information such as a statement that the product should not be used for more than three weeks without medical advice. This protects users of meal replacements without other food from inadvertent malnutrition.

In the United States, the term "meal replacement" is not defined in federal Food and Drug Administration regulations, but generally refers to a calorie-controlled, prepackaged product in the form of a bar or beverage (ready to drink or powder), that replaces a regular meal. Meal-replacement products usually provide 200 to 250 calories per serving, are fortified with more than 20 vitamins and minerals at "good" or "excellent source" levels and often bear nutrient content claims, such as percent fat free and reduced sugar. Meal replacement products can be regulated as conventional or functional foods. In Canada, meal replacements are regulated by the Canadian Food Inspection Agency and must meet minimum calorie, protein and vitamin requirements, causing some American products to be rejected.

Negative-calorie food

A negative-calorie food is food that supposedly requires more food energy to be digested than the food provides. Its thermic effect or specific dynamic action—the caloric "cost" of digesting the food—would be greater than its food energy content. Despite its recurring popularity in dieting guides, there is no scientific evidence supporting the idea that any food is calorically negative. While some chilled beverages are calorically negative, the effect is minimal and drinking large amounts of water can be dangerous.

Protein–energy malnutrition

Protein–energy malnutrition (PEM) is a form of malnutrition that is defined as a range of pathological conditions arising from coincident lack of dietary protein and/or energy (calories) in varying proportions. The condition has mild, moderate, and severe degrees.

Types include:

Kwashiorkor (protein malnutrition predominant)

Marasmus (deficiency in calorie intake)

Marasmic kwashiorkor (marked protein deficiency and marked calorie insufficiency signs present, sometimes referred to as the most severe form of malnutrition)PEM is fairly common worldwide in both children and adults and accounts for 6 million deaths annually. In the industrialized world, PEM is predominantly seen in hospitals, is associated with disease, or is often found in the elderly.Note that PEM may be secondary to other conditions such as chronic renal disease or cancer cachexia in which protein energy wasting may occur.

Protein–energy malnutrition affects children the most because they have less protein intake. The few rare cases found in the developed world are almost entirely found in small children as a result of fad diets, or ignorance of the nutritional needs of children, particularly in cases of milk allergy.

Tab Energy

Tab Energy is marketed as a low calorie energy drink named after Tab, Coca-Cola's original low-calorie cola brand. While it shares the Tab name, it is not a cola product like the original Tab. Fashion Week Daily describes it as a “sweet and sour beverage” with a taste “reminiscent of a liquid Jolly Rancher”. It is sweetened with sucralose (rather than saccharin), is pale pink, and lightly carbonated.

It is packed in 10.5-US-fluid-ounce (311 ml) slim cans (with a shape similar to the can used for Red Bull). The New Yorker notes that the original Tab has 31 milligrams of caffeine and less than 1 calorie (4.2 kJ) per serving, while Tab Energy has 95 milligrams of caffeine and 5 calories (21 kJ). (It also contains 785 mg taurine, 116 mg ginseng extract, 19 mg carnitine, and 0.90 mg guarana extract, according to the can.)

The drink is currently being targeted and advertised towards a female market as illustrated by the pink color theme and slogan 'Fuel to be Fabulous'. The song used in the American version of the commercial is "Cobrastyle" by the Teddybears.

Tab Energy is also available in Mexico since December 2006, in New Zealand since February 26, 2007, and in Spain since September 2008 under the name Tab Fabulous. This drink is currently being taken off the market by Coca-Cola.

Very-low-calorie diet

Very low calorie diet (VLCD), or sometimes called starvation diet, is a diet with very or extremely low daily food energy consumption. It is defined as a diet of 800 kilocalories (3,300 kJ) per day or less. VLCDs are formulated, nutritionally complete, liquid meals containing 800 kilocalories or less per day. VLCDs also contain the recommended daily requirements for vitamins, minerals, trace elements, fatty acids and protein. Carbohydrate may be entirely absent, or substituted for a portion of the protein; this choice has important metabolic effects. The VLCD products are usually a powder which is mixed with water or another low-food-energy liquid. The VLCD is prescribed on a case to case basis for rapid weight loss (about 1.5 to 2.5 kilograms or 3 to 5 pounds per week) in people with body mass index (BMI) of 30 and above. The health care provider can recommend the diet to a patient with a BMI between 27 and 30 if the medical complications the patient has due to being overweight present serious health risks. It results in 4% more weight loss over the short term as compared to control.

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