Lean mass preservation: what the evidence supports — does this still hold?

Ultrasound: thickness of subcutaneous fat at specific sites. Less standardised than DXA and operator-dependent. Useful as a supplementary measure but not as a primary method.

For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use.

Coming back to post #15, because the follow-up matters more than the original answer.

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.

Worth separating two things that post #15 runs together.

Changes during titration: measuring body composition during active titration is less useful than measuring after dose is stable. Titration causes fluid shifts that confound body composition.

post #19 is right about the mechanism and I think understates the practical bit.

Maintenance phase: tracking body composition during maintenance (weight stable) is different from tracking during active loss. Changes are smaller and precision becomes more important.

Resting metabolic rate: body composition affects metabolic rate. As fat mass decreases and lean mass is maintained, metabolic rate is usually maintained better than with simple weight loss alone.

Visceral fat: DXA does not distinguish visceral (organ-associated) fat from subcutaneous fat. That distinction might matter but requires different imaging to measure.

Picking up post #20: that is the part I would want checked first.

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.

Coming back to post #22, because the follow-up matters more than the original answer.

Bioelectric impedance analysis: less precise than DXA and strongly affected by hydration state. Not reliable for detecting month-to-month changes. Useful for trend over years if done consistently.

post #24 is right about the mechanism and I think understates the practical bit.

Visceral fat: DXA does not distinguish visceral (organ-associated) fat from subcutaneous fat. That distinction might matter but requires different imaging to measure.

Practical note that does not fit anywhere else. Whatever you conclude from this topic, write down what you did and when. The single most useful thing in your own records is not any individual result; it is that they are dated and consecutive.

Bioelectric impedance analysis: less precise than DXA and strongly affected by hydration state. Not reliable for detecting month-to-month changes. Useful for trend over years if done consistently.

I read post #26 twice before replying, because I had assumed the opposite.

Ultrasound: thickness of subcutaneous fat at specific sites. Less standardised than DXA and operator-dependent. Useful as a supplementary measure but not as a primary method.

post #28 answers the question as asked. The question underneath it is different.

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.

On post #26 — agreed on the reasoning, with one qualification.

Resting metabolic rate: body composition affects metabolic rate. As fat mass decreases and lean mass is maintained, metabolic rate is usually maintained better than with simple weight loss alone.