sarah.morrison said:

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…

This is where I part company with the consensus forming above. I think this board over-worries about lean mass. Some lean loss is obligatory — you need less muscle to move a smaller body, and preserving mass you no longer need is not a health outcome. The question is whether strength and function held, and mine did.

amsterdam_pete said:

Two DEXA scans eleven months apart: down 24kg total, of which the scan says 6kg was lean.

Sharing my comprehensive lab data relevant to lean mass:

Protocol: Semaglutide 2.4mg/wk, resistance training 3x/week, protein 1.4g/kg/day.

The improvements in lean mass are clearly reflected in these numbers. The inflammatory marker reduction (hsCRP) is particularly striking.

Dr.ObesityLA said:

I think this board over-worries about lean mass.

Physical therapist weighing in on lean mass. I work with bariatric and metabolic patients daily.

The resistance training evidence is critical here:

The Lundgren 2024 JAMA paper[1] showed that structured resistance training preserved 73% more lean mass in GLP-1 patients vs medication alone. When discussing lean mass, we MUST include the exercise component.

My minimum prescription: 3x/week compound movements (squat, deadlift, press, row), progressive overload, 7-10K steps/day, and 1.2-1.6g protein/kg/day.

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

What fraction of loss being lean mass is actually normal, because the numbers quoted here range from 10% to 40% and cannot all be right?

Closing the loop on my own question.

Second scan under matched conditions, six months apart, same time of day: the lean number came back nearly a kilo higher than the panic scan. Strength was up throughout.