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c/glp1muscle·posted 10 days ago by u/hamza_zielinski

[Discussion] FFMI not weight, or you will celebrate losing muscle

Discussion Clean Column ×2

Posting this as a discussion rather than a claim: FFMI not weight, or you will celebrate losing muscle.

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.

Fat-free mass index is a ratio of fat-free mass to height squared. It moves when either term does, which makes it awkward to interpret during active weight change.

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

Screenshot none of this. Read the whole thread, including the parts where I am told I am wrong.

248 up / 43 down85% upvoted26 commentsid 4gdlof19 Jul 2026

26 comments

19 in this archive, depth 5

best — the order this archive was captured in

u/nayeli_fonseca33 points·10 days ago

Nothing here is a training or nutrition prescription. Targets and programmes are matters for somebody who knows your history and your training background.

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[deleted]24 points·9 days ago

[deleted]

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u/tuva_kirchner11 points·9 days ago

losing weight slower does not automatically preserve more lean mass

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u/hamza_zielinskiOP8 points·9 days ago

That protein figure is grams per day, not grams per kilogram. Different claim entirely.

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u/yara_mensah42 points·9 days ago

the appetite effect makes eating enough protein a logistics problem

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u/protein_first_pnutrition13 points·9 days ago

Agreed on the error margin. Quoting a DEXA to one decimal implies a precision the method does not have.

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u/ferran_dahlberg-6 points·9 days ago

nothing on this board is a training or nutrition prescription

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u/viktor_laurent5 points·9 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/dexa_twice_yearlybody comp2 points·8 days ago

Agreed — protein and resistance training. Everything else in these threads is a rounding error on those two.

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u/maintenance_mode_maxmaintenance3 points·8 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/alcohol_aversion33 points·10 days ago

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

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u/nikhil_asante16 points·9 days ago

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

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u/greta_perrin19 points·9 days ago

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.

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u/vito_chowdhury8 points·9 days ago

Cosigning that protein gets harder precisely when appetite drops. That is the actual difficulty and it is logistical.

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u/greta_lokken5 points·9 days ago·edited

Correction: those scans are from different machines, and the difference you are describing is within the measurement error.

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u/joaquin_wojcik3 points·8 days ago

a single DEXA is a number, two is a comparison, three is a trend

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u/reflux_report16 points·8 days ago·edited

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

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u/liv_dumitru6 points·8 days ago

Not convinced by that DEXA comparison. Different machine, different protocol, and the difference is inside the error.

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u/halima_mbeki9 points·10 days ago

I would not change the programme on the strength of one scan. The measurement error is larger than the effect you are reacting to.

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About c/glp1muscle

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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