One calorie is defined as the amount of heat required to raise the temperature of one gram of water from 14.5°C to 15.5°C at one atmosphere of pressure. It it used as a unit of energy, although it is a non SI unit. It is commonly used as a unit of measurement in nutrition. It's first usage was by Nicolas Clément in 1824.
- ↑ Hargrove J. History of the Calorie in Nutrition. American Society for Nutrition. 2006;136(12):2957-2961.