Peter Attia's energy expenditure measurements from room calorimetry and doubly labeled water overlapped closely, even on a ketogenic diet.

“so when I did this I did several days in several chambers and then separately did the LW I was kind of amazed at how closely they overlapped of course it was hard to replicate my chamber activity in the real world because there's so much more you know movement outside of the chamber but they were surprisingly inline which is interesting because at the time I was on ketogenic diet which there's a lot of things that could be changing there”