This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
I would put moderate confidence on the mainstream reading of Lean mass preservation and no more. That is not scepticism for its own sake; it is where the sourcing actually stops.
Picking up post #29: that is the part I would want checked first.
The question underneath Lean mass preservation is usually "how would I tell?" rather than "what is true?", and that one has a method attached to it.
Write down what you would expect to see under each hypothesis before you collect anything. If they predict the same observation, collecting it will not help.
DXA on the same machine with the same technician has a least significant change for lean mass of roughly a kilogram, sometimes more. Below that, two scans are the same scan.
Worth reading the earlier posts in this thread before acting on mine.
Muscle gained during a deficit is possible in specific circumstances and is not the usual case, and the published evidence is clear about which circumstances.
That is one dataset and I would not build a rule on it.
The confident answers on Lean mass preservation and the well-sourced answers are not the same answers, which is the most useful thing I have learned reading this category.
I had written a reply contradicting post #34 and deleted it. Here is what survived.
Small correction to my own earlier position on Lean mass preservation. I had the units the wrong way round, which changes the conclusion by an order of magnitude and therefore changes it entirely.
Photographs under fixed lighting and posture are a genuine record and are the hardest of these to standardise.
Answering the question post #37 raises rather than the one it answers.
The most useful protocol is the one you will actually repeat identically. An imperfect measurement repeated consistently beats a better one repeated carelessly.
Preserving lean tissue during a substantial deficit depends on protein intake and a resistance stimulus, and the evidence for both is reasonably strong.
Lean mass preservation looks different depending on whether you are reading the primary literature or the summaries of it, and the difference is not in our favour.
Small methodological point on Lean mass preservation: repeating a measurement is cheap and resolves most of what is being argued about here at no cost to anyone.
Post #42 answers the question as asked. The question underneath it is different.
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.
I read post #40 twice before replying, because I had assumed the opposite.
Trying to state the Lean mass preservation position in a way that someone who disagrees would recognise as fair, because I do not think the version in this thread passes that test.
Lean mass preservation sits at the boundary between what this community can usefully discuss and what it cannot, and I think it falls on the discussable side, narrowly.
Post #44 and I disagree about the size of the effect, not about the direction.
Neither method is capable of detecting the month-to-month changes that people report detecting month to month.
Narrowing post #46, because the general version has more than one answer.
Absolute lean mass and lean mass as a proportion move differently and answer different questions. Report both or say which.
Adding the measurement that post #46 says would settle it.
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.
Something worth flagging about Lean mass preservation: the strongest-sounding claims in this thread are the ones with no source attached, which is the usual pattern and not a coincidence.
I have three months of notes on Lean mass preservation and the honest summary is that the trend is real and the week-to-week numbers are noise. I nearly drew the opposite conclusion from the first fortnight.
That reframing is the whole thing. The facts I already had.
Narrowing post #51, because the general version has more than one answer.
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.
Where I part company with post #51, and it is a narrow parting.
Photographs under fixed lighting and posture are a genuine record and are the hardest of these to standardise.
Lean mass preservation has a well-known answer and a correct answer, and the interesting work is establishing that they are the same. Nobody has done that here yet.
The documentation on Lean mass preservation is better than this thread and I say that as someone who has posted in the thread.
Comparison to published data: the trials reported mean fat and lean mass changes. Individual results vary around that mean. Being above or below average is not a sign of something wrong.
Not disagreeing with anyone above, just adding the bit I keep having to look up.
Following this. I have the same question and no better information than the first post.