I vaguely remembered that the doubly-labeled water method was pretty neat, but I looked it up and it is as neat as I remember: https://en.wikipedia.org/wiki/Do

I vaguely remembered that the doubly-labeled water method was pretty neat, but I looked it up and it is as neat as I remember: https://en.wikipedia.org/wiki/Doubly_labeled_water#Mechanism_of_the_test https://en.wikipedia.org/wiki/Doubly_labeled_water#Mechanism... It's like plugging yourself into a power meter, except for cellular respiration