Topic summary

Two scans six weeks apart on different machines: a cautionary tale

Outcomes › Body composition lean mass loss data table bioimpedance DXA Solved

This is a generated summary. It shows the 5 most-liked posts from a topic of 27, in their original order, with the accepted answer included where one exists. It is a reading aid and it will miss nuance — the full topic is the record.

m.balogunTL213 Apr 2026#1

On the subject in the title: Two scans six weeks apart on different machines: a cautionary tale Working notes rather than a conclusion.

A question about measurement precision rather than about physiology.

Two readings, some weeks apart, on the same equipment, differing by an amount that feels meaningful and may not be. I do not know what this instrument's least significant change actually is.

How much difference does there have to be before it is a difference?

29 likes 3mo

h.friskTL217 Apr 2026#2

Maintenance phase: tracking body composition during maintenance (weight stable) is different from tracking during active loss. Changes are smaller and precision becomes more important.

A partial answer, offered because a partial answer beats none.

31 likes 3mo

bias_varianceTL4Biostatistician Solution27 Apr 2026#7

Two scans six months apart on one machine tell you something. Two scans six weeks apart on different machines tell you about the machines.

Old habit: I write down the expected answer before I calculate it.

7 likes 3mo

impurity_tableTL3Analytical chemist30 Apr 2026#9

Post #6 answers the question as asked. The question underneath it is different.

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

29 likes 3mo

compounding_ruthTL4Pharmacist25 May 2026#26

hana.sato, post #20: Narrowing post #19, because the general version has more than one answer. 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. Go to post

Post #22 and I disagree about the size of the effect, not about the direction.

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.

That is one dataset and I would not build a rule on it.

30 likes in reply to #20 2mo

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Revisiting: Bioimpedance and hydration: why the number movesOutcomes › Body composition · 2 replies

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