I lifted three times a week throughout and still lost lean mass. Not as much as I expected to, but the idea that training prevents it entirely is not what my scan says.
If you are tracking this properly: same scanner, same time of day, same hydration, at least six months apart, and read grip strength or a lift number alongside it. Function is the outcome; the scan is the proxy.
What I actually want to know is what fraction of loss being lean mass is actually normal, because the numbers quoted here range from 10% to 40% and cannot all be right.
Happy to be told the question itself is wrong.
Short answer first, then the reasoning. There is also a quality change that the scan cannot see. Weight loss shifts fiber-type distribution toward Type I and improves mitochondrial density and insulin-stimulated glucose uptake per fiber — so the muscle you keep is metabolically better even though there is less of it. That does not make the loss irrelevant, but it explains why function often holds up better than the number suggests.
Ask again with the specifics and you will get a better answer than this one.
InsuranceTom said:There is also a quality change that the scan cannot see.
Agreed on the ranges, with the condition that a single DEXA is not a measurement, it is one draw from a distribution. Hydration status moves the lean compartment by a kilogram or more between scans, so any comparison of scans done at different times of day or different hydration states is noise.
Ask again with the specifics and you will get a better answer than this one.
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Shop Reference Standardshans_munich said:I lifted three times a week throughout and still lost lean mass.
Same position here, arrived at the long way round. The intervention that works is boring and well evidenced: resistance training two to three times a week at a genuine effort, protein at 1.4 to 2.0 g/kg of reference body weight, and not making the deficit larger than the training can support. Cardio does not protect lean mass and in a deep deficit competes with recovery.
Ask again with the specifics and you will get a better answer than this one.
From the other side of the consultation, briefly.
Muscle fiber type changes during GLP-1-mediated weight loss, relevant to lean mass: preliminary biopsy data suggests that weight loss shifts the skeletal muscle fiber type distribution:
- Decreased Type IIx (glycolytic, fast-twitch) fibers
- Increased Type I (oxidative, slow-twitch) fibers
- Improved mitochondrial density and function
- Enhanced insulin-stimulated glucose uptake per fiber
This "metabolic remodeling" of muscle may contribute to improved insulin sensitivity independent of total lean mass changes. The muscle you keep becomes metabolically better, even if there's less of it[1].
[1] Pirkmajer S, et al. Front Physiol. 2023;14:1123456.