text: Antoine Lavoisier noted in 1780 that heat production, in some cases, can be predicted from oxygen consumption, using multiple regression. Indirect calorimetry, as we know it, was developed around 1900 as an application of thermodynamics to animal life. Although the development of indirect calorimetry dates back over 200 years, its greatest use has been in the last two decades with the development of total parenteral nutrition, interdisciplinary nutrition support teams, and the production of portable, reliable, relatively inexpensive calorimeters.