Comment by zenlf
3 years ago
This is interesting. However I would love to learn more about the “doubly labeled water method”. For example, how accurate is the test result? What’s the individual variance? Do animals and humans react the same way to it?
It’s important because all the findings seem to be based on it, but the specifics are not discussed.
I got curious and did a bunch of research.
It relies on the fact that carbon dioxide is transmitted from tissues to lungs in blood as carbonic acid. The carbonic acid is formed by water and carbon dioxide.
It seems extremely accurate as long as you believe the distribution of labeled water equalizes in the body. You can readily see exactly how much labeled oxygen was lost via CO2 (via the carbonic acid reaction).
As long as metabolism and blood transport works the same in all animals, seems reliable.