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c/glp1muscle·posted 12 days ago by u/step_count_stan

[Data] BIA vs DEXA on the same day, 6% apart, pick a method and stay with it

Data Well Actually ×9

Thinking out loud about this: BIA vs DEXA on the same day, 6% apart, pick a method and stay with it.

Hard numbers: 6%. Anything softer than that is flagged as an impression.

Some lean mass loss accompanies weight loss in any deficit. Resistance training and adequate protein intake are the two interventions with the best evidence for limiting the proportion.

DEXA has a meaningful coefficient of variation, and it differs between machines and protocols. Comparing scans from different clinics adds a systematic offset that is invisible on the report.

Please do not ask me what dose you should be on. I genuinely do not know and neither does anyone else here.

440 up / 74 down86% upvoted25 commentsid 4qd7de17 Jul 2026

25 comments

17 in this archive, depth 6

best — the order this archive was captured in

u/rina_nascimento42 points·12 days ago

Strength retention is an imperfect but free longitudinal proxy: it is affected by neural factors and by being in a deficit, so it tracks tissue change loosely rather than exactly.

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u/sanne_novak30 points·12 days ago·edited

Disagree — slower loss does not automatically preserve lean mass. Protein and training do the work, not the rate on its own.

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u/long_post_larry24 points·12 days ago

Push back: strength dropping in a deficit is not the same as lean mass loss. Related, not identical.

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u/greta_lokken19 points·12 days ago

Small fix — that is fat-free mass, not muscle mass. The scan cannot separate them the way the post assumes.

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u/throwaway_wl20268 points·11 days ago

Tracked grip strength and three lifts monthly. Cheaper than scanning and directionally the same answer.

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u/greta_lokken6 points·11 days ago

Correcting myself upthread: 4 months between scans, not the figure I gave.

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u/emil_okwuosa3 points·11 days ago

Hydration status and fasting state affect the lean mass estimate. Standardising both is the difference between a comparison and a coin toss.

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u/priya_weiss15 points·12 days ago

Same. Volume over novelty. Changing programme every six weeks cost me a year.

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u/reflux_report7 points·11 days ago

Resistance training, and at what frequency?

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[deleted]11 points·11 days ago

[deleted]

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u/vito_chowdhury16 points·11 days ago

Fasted and hydrated the same way for both scans?

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u/step_count_stanOP0 points·10 days ago

Have the lifts held, dropped, or moved around?

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u/alcohol_aversion12 points·11 days ago

Yes. Lean mass change during weight loss is expected; the useful question is the proportion, not whether it happens.

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u/amylin_amyamylin14 points·12 days ago

Are you comparing against your own baseline or against a published average?

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u/step_count_stanOP8 points·11 days ago

How many weeks between the two scans?

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u/usp_appendixcompendial12 points·11 days ago·edited

Three scans over eighteen months, same machine, same conditions. Only the third one made the first two interpretable.

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u/hamza_zielinski-9 points·11 days ago

protein intake gets harder exactly when appetite drops

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Lean-mass retention during rapid weight loss: protein targets, resistance-training minimums, DEXA and BIA measurement reality, FFMI tracking, and the sarcopenia question that nobody funded a proper trial for.

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