Lean mass preservation: what the evidence supports

Lean mass preservation: what the evidence supports Writing it up because I had to work it out twice and would rather nobody else did.

Trying to work out what would count as evidence on lean mass preservation, before collecting any. This is the part I usually skip and it is the part that makes the rest useful.

If two explanations predict the same observation, observing it does not help. So: what observation would separate them?

That is clearer than the version I had in my head. Thank you.

Neither method is capable of detecting the month-to-month changes that people report detecting month to month.

Not a strong opinion, just a consistent one.

I would keep lean mass preservation and the decision it usually gets used for separate in this thread. They are related and they are not the same question, and merging them is why the last one went badly.

Precision versus accuracy: the precision you need depends on what question you are answering. "Am I losing fat?" requires less precision than "Is my lean mass preservation within the expected range?"

Two people can read the same figure differently here and both be reasonable.

Lean mass loss during rapid weight reduction: depends on protein intake, resistance training volume, and total energy deficit. Adequate protein and maintaining training intensity both help preserve lean mass.

One of those cases where knowing the mechanism does not help the decision.

Everything in post #5 holds. The case it does not cover is the one I have.

An honest declaration on lean mass preservation: I have a prior here and it is strong enough that you should weight what I say downward. Stating it rather than hiding it.

Percentage body fat is a ratio, so it changes when either component changes. A rising percentage during weight loss is arithmetic before it is physiology.

Noting that the question and the thing people usually mean by it are different.

Photographs under fixed lighting and posture are a genuine record and are the hardest of these to standardise.

I would call that likely rather than established.

Preserving lean tissue during a substantial deficit depends on protein intake and a resistance stimulus, and the evidence for both is reasonably strong.

None of the above is medical advice and I am not qualified to give any.

Picking up post #10: that is the part I would want checked first.

What I want from this lean mass preservation thread is the list of things that would need to be true for the claim to hold. If we can write that list, we can check it.

Lean mass in these measurements includes water, so a change in hydration appears as a change in lean mass.

If it helps: the failure mode here is usually boring rather than dramatic.

DXA (dual-energy X-ray absorptiometry): the standard for body composition in research. Precision is roughly ±1 kg for lean mass. Two scans six months apart on the same machine with the same technician give you useful information. Two scans six weeks apart on different machines tell you about the machines.

It is the sort of thing that seems obvious in retrospect and was not at the time.

I had written a reply contradicting post #12 and deleted it. Here is what survived.

Lean mass preservation: I have looked for the primary source twice and failed twice. Either it does not exist or it is somewhere I do not know to look, and I would like to know which.