Dr.PeteFamMed said:

Worth stating the units and the reference range whenever you post a number here.

This is exactly what I could not find anywhere else. Taking it to my next appointment.

From the other side of the consultation, briefly. The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either. Those three things can all be true at once, and most arguments here are two people holding different parts of that.

Moderator note: good thread. Keeping it here rather than moving it, because the question is general enough to be useful.

Dr.LipidDallas said:

The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either.

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

Adding the numbers, since they settle part of this. The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the same conditions. Nobody wants that answer and it is still the answer.