03/21/2026
What the study actually says:
In the STEP 1 DXA substudy, semaglutide 2.4 mg led to ~15% total weight loss, with ~40% of that loss classified as lean mass.
That number stands out, and you can see it in the graph.
Most interventions cluster around the ~25% “diet benchmark”
(diet alone, bariatric surgery, tirzepatide), meaning the proportion of lean mass loss is largely similar to traditional weight loss.
Semaglutide sits to the right as an outlier.
But that needs context.
DXA “lean mass” includes water, organ tissue, and connective tissue, not just skeletal muscle. Some of that signal reflects normal physiologic shifts during weight loss.
And importantly, STEP 1 did not require resistance training or protein targets, both of which are key for preserving muscle.
So yes, the graph is accurate:
👉 Most weight loss, including GLP-1s, follows the expected proportion seen with dieting
👉 Semaglutide appears higher in that dataset
The number is real. The interpretation is where it matters.
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Study referenced:
Wilding JPH et al. NEJM. 2021 (STEP 1)
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