Second pass at: Circumference measurements as a poor man's composition estimate

Post #3 is the version of this I will quote in future. One addition.

Resting metabolic rate: body composition affects metabolic rate. As fat mass decreases and lean mass is maintained, metabolic rate is usually maintained better than with simple weight loss alone.

The general answer and the answer for your case may diverge here.

Building on post #7 rather than restating it.

Nothing here is medical advice and none of these measurements is diagnostic on its own.

I have said this before in a thread nobody could find, so it is worth repeating.

Coming back to post #10, because the follow-up matters more than the original answer.

A note on scope: what I am saying about Circumference measurements applies to the case in the first post and I would not extend it further without checking.

Worth separating two things that post #23 runs together.

Bone mineral density changes with substantial weight loss are measurable and slow, and are one of the better reasons to have a baseline scan.

If that reads as pedantic, it is, and it has saved me twice.

DXA (dual-energy X-ray absorptiometry): the standard for body composition in research. Precision is roughly ±1 kg for lean mass. Two scans six months apart on the same machine with the same technician give you useful information. Two scans six weeks apart on different machines tell you about the machines.

One more caveat and then I will stop qualifying: the sample selected itself.

Taking post #38 at face value and following it one step further.

Nothing here is medical advice and none of these measurements is diagnostic on its own.

Not the whole picture, but the part of it I can speak to.

Post #45 is right about the mechanism and I think understates the practical bit.

The documentation on Circumference measurements is better than this thread and I say that as someone who has posted in the thread.

Bone mineral density changes with substantial weight loss are measurable and slow, and are one of the better reasons to have a baseline scan.

A guess, clearly labelled as one.

The most useful protocol is the one you will actually repeat identically. An imperfect measurement repeated consistently beats a better one repeated carelessly.

Adding the caveat now so it does not have to be extracted later.