Taking the question as asked, rather than the general version of it. 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.

I would rather be corrected than agreed with, if it comes to it.

KevinCompounds said:

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…

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.

That is the short version; the long version is somebody else's post.

wendy_avl said:

Two DEXA scans eleven months apart: down 24kg total, of which the scan says 6kg was lean.

Can confirm the pattern wendy_avl describes. The honest range is roughly 20 to 40% of total loss as lean mass without deliberate resistance training, and roughly 10 to 20% with it plus adequate protein. Both numbers need a caveat that matters: "lean mass" on a DEXA is not muscle. It includes water, glycogen and the lean fraction of organs, and glycogen alone carries about three grams of water per gram. A large early lean drop is mostly the glycogen and water going, which is why the first scan flatters and the second is the honest one.

Adding the clinical framing, because it changes how the question reads.

Regarding lean mass: I accidentally injected my dose intramuscularly instead of subcutaneously last week (went in at wrong angle, too deep). Called my pharmacist — they said it's not dangerous but may absorb faster, potentially causing more GI effects.

Sure enough, had worse nausea that day. Lesson learned: pinch the skin properly and use the right needle length for your body composition.