This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Neither method is capable of detecting the month-to-month changes that people report detecting month to month.
That is a fair summary of where the discussion has got to.
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.
Lean mass in these measurements includes water, so a change in hydration appears as a change in lean mass.
I am reporting what happened, not recommending it.
Post #34 is right about the mechanism and I think understates the practical bit.
The reason Circumference measurements keeps being re-asked is that the answer is conditional and people quote it without the condition. It is not that the answer is unknown.
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.
Comparing a body composition result against a population reference is a different exercise from tracking your own change, and the second is what most people want.
Speaking for myself and not for anyone else who has posted here.
I had written a reply contradicting post #37 and deleted it. Here is what survived.
Changes during titration: measuring body composition during active titration is less useful than measuring after dose is stable. Titration causes fluid shifts that confound body composition.
Percentage body fat is a ratio, so it changes when either component changes. A rising percentage during weight loss is arithmetic before it is physiology.
This is the sort of thing that ought to be settled and apparently is not.
Circumference measurements has a well-known answer and a correct answer, and the interesting work is establishing that they are the same. Nobody has done that here yet.
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.
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.
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.
Post #50 put the caveat in the right place and I want to underline it.
Circumference measurements looks different depending on whether you are reading the primary literature or the summaries of it, and the difference is not in our favour.
Comparing a body composition result against a population reference is a different exercise from tracking your own change, and the second is what most people want.
The confident version of this sentence would be wrong, so here is the hedged one.
Second this, and I would have said it less carefully.
Post #52 is the version of this I will quote in future. One addition.
Careful with the language on Circumference measurements. "Not detected" and "not present" are different findings and the first is a statement about the method.
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.
I would put the burden of proof on the interesting explanation, not the dull one.
Circumference measurements: I have looked for the primary source twice and failed twice. Either it does not exist or it is somewhere I do not know to look, and I would like to know which.
Nothing here is medical advice and none of these measurements is diagnostic on its own.
That has held every time I have looked, which is not the same as always.
An update on my earlier Circumference measurements post: the pattern held for another six weeks and then stopped, which I did not predict and cannot explain.