In one uncontrolled study, lean mass fell 3 kg and then held
In 106 French adults on 2.4 mg semaglutide, lean mass fell 3 kg by month seven and then held steady while fat kept going. There was no comparison group.
What the study found
Lean mass fell 3kg in seven months, then stopped falling
The shape of the loss may matter more than its size. In 106 French adults on 2.4mg semaglutide, lean mass fell 3kg by month seven and then held steady while fat kept going, grip strength rose 4.5kg, and the share carrying too little muscle for their body size fell from 49% to 33%.
The caveat · Nutrition care came with the drug
There was no control group and no randomisation, so nothing separates the drug from the specialist nutrition care these patients also received, or from people simply moving more as they got lighter. Grip strength rising during weight loss is partly expected because a lighter body is easier to move, and the study did not adjust for that. Mean body mass index was 46.3, far heavier than the trial populations. Calling 3kg preserved is the authors' reading of a real loss.
What we don't know
What this study can show is how lean mass fell over time, stopping by month seven. With nobody off the drug measured alongside, it cannot show that semaglutide, rather than anything else, preserved it.