Review of RMR.

For me it was an opportunity to investigate what constitutes energy in the body. As you point out calorimetry is basically O2 in and CO2 out giving an estimate of the amount of energy utilized. This to me points out that the estimate is based on mitochondrial function where O2 is taken in (with glucose) and CO2 produced (with ATP). However I did find an interesting article, “Beyond mitochondria, what would be the energy source of the cell?” which challenges the assumption that this is the only energy produced (1). In our basic texts, the workings of the mitochondria seem complex but understood. 

This article points out that “For the apparently well studied metabolic process Krebs cycle, which was described as early as 1937 and is found in nearly every biology and chemistry curriculum, there is a considerable disagreement between at least five databases. Of the nearly 7000 reactions contained jointly by these five databases, only 199 are described in the same way in all the five databases. Thus to try to integrate chemical energy from melanin with the supposedly well-known bioenergetic pathways is easier said than done; and the lack of consensus about metabolic network constitutes an insurmountable barrier.”

These authors concluded based on research of research on melanins ability to transform photons of light into chemical energy that melanin may represent over 90% of cell energy requirements (!).

Herrera, Arturo S., Maria Del C A Esparza, Ghulam Md Ashraf, Andrey A. Zamyatnin, and Gjumrakch Aliev. “Beyond Mitochondria, What Would Be the Energy Source of the Cell?” Central Nervous System Agents in Medicinal Chemistry 15, no. 1 (2015): 32–41.