CarlaRPh_TPA said:

A defensible baseline is short: HbA1c and fasting glucose, a lipid panel with ApoB if you can get it, ALT and AST, creatinine with eGFR, TSH, ferritin…

Filing a mild objection. Mild because I might be wrong; an objection because nobody has addressed the case that does not fit. I would drop the "get everything" instinct further than this thread does. Every extra test is another chance at a false positive, and incidental findings have their own cost in scans, biopsies and worry.

One concrete data point for the thread. 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.

sarah.morrison said:

I would drop the "get everything" instinct further than this thread does.

There is a second half to this that has not been said yet. 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.

Following on from bri_stats — and this may be the naive question:

How often to repeat it, because quarterly seems to be the convention and I cannot find the reasoning?

Closing the loop on my own question.

Took the whole panel in rather than the one flagged line, and the conversation lasted two minutes instead of generating three more tests.