On this Wikipedia the language links are at the top of the page across from the article title. The calorie is a unit of energy that originated from the obsolete caloric theory of heat. For historical reasons, two main calories in 3 ounces of chicken breast of “calorie” are in wide use.

In nutrition and food science, the term calorie and the symbol cal almost always refers to the large unit. This unit was used by U. Joseph Howard Raymond, in his classic 1894 textbook A Manual of Human Physiology. In 1879, Marcellin Berthelot distinguished between gram-calorie and kilogram-calorie, and proposed using “Calorie”, with capital “C”, for the large unit. Already in 1928 there were serious complaints about the possible confusion arising from the two main definitions of the calorie and whether the notion of using the capital letter to distinguish them was sound. The joule was the officially adopted SI unit of energy at the ninth General Conference on Weights and Measures in 1948. The alternate spelling calory is considered nonstandard and dated.

The amount of energy equal to exactly 4. The amount of energy required to warm one gram of air-free water from 3. The amount of energy required to warm one gram of air-free water from 14. Experimental values of this calorie ranged from 4. The CIPM in 1950 published a mean experimental value of 4. 1855 J, noting an uncertainty of 0. The amount of energy required to warm one gram of air-free water from 19.

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 was later redefined as 4. C calorie and the thermochemical calorie. Until 1948, the latter was defined as 4. 184 J was chosen to have the new thermochemical calorie represent the same quantity of energy as before. In a nutritional context, the “large” unit is used almost exclusively.

In the United States, most nutritionists prefer the unit kilocalorie to the unit kilojoules, whereas most physiologists prefer to use kilojoules. In the majority of other countries, nutritionists prefer the kilojoule to the kilocalorie. On nutrition facts labels in the European Union, energy is expressed in both kilojoules and kilocalories. In the United States and Canada, labels use “Calories”, referring to the large unit. In China, only kilojoules are given. Dieting is the practice of eating food in a regulated way to decrease, maintain, or increase body weight, or to prevent and treat diseases such as diabetes and obesity. The lingering use in chemistry is largely due to the fact that the energy released by a reaction in aqueous solution, expressed in kilocalories per mole of reagent, is numerically close to the concentration of the reagent, in moles per liter, multiplied by the change in the temperature of the solution, in kelvin or degrees Celsius.

Academic Press Dictionary of Science and Technology. Definition of calorie noun from the Oxford Advanced American Dictionary”. What should my daily intake of calories be? Calculating Calories by Burning Gummy Bears to Death”.

Does the history of food energy units suggest a solution to “Calorie confusion”? International Standard ISO 31-4: Quantities and units, Part 4: Heat. Other units given for information, especially regarding the conversion factor. Excursion in Chemical Thermodynamics, from the Past into the Future”. IT calorie and the thermochemical calorie are completely independent of the heat capacity of water.