STEP UP MRI substudy reports semaglutide 7.2 mg body composition at EASD 2025
An MRI substudy of STEP UP reported a smaller lean-tissue share of weight loss on semaglutide than DXA analyses have, a reminder that the measurement method shapes muscle-loss headlines.
An MRI-based substudy of the STEP UP trial reported how weight loss on semaglutide 7.2 mg and 2.4 mg splits between fat tissue and lean tissue. The results were given as an oral presentation dated September 25, 2025, at the European Association for the Study of Diabetes (EASD) 2025 meeting, according to the presentation listing posted on Novo Nordisk's science hub [1].
The substudy measured body composition with magnetic resonance imaging (MRI) rather than DXA scans [1]. That choice changed the answer. The presentation reports a lower lean-tissue proportion than DXA-based analyses have found, the listing states, which it frames as evidence that the measurement method drives the muscle-loss numbers that get reported [1]. Put plainly, the share of total weight lost that came from lean tissue was smaller when measured by MRI than when measured by DXA [1].
The specific figures are not in the posting. It does not give the percentage of weight loss that came from fat versus lean tissue, the number of participants who were scanned, how long the substudy ran, or any breakdown by age [1]. Those details have not been reported in the material posted so far [1].
Two doses appear in the substudy: semaglutide 7.2 mg and semaglutide 2.4 mg [1]. Semaglutide is the molecule in Ozempic, Wegovy and Rybelsus. The posting does not say how many people received each dose, whether the substudy included people with diabetes, or how the two dose groups compared with each other on body composition [1].
The presentation is listed as an oral presentation titled for STEP UP body composition, with the date September 25, 2025 in the file name [1]. Whether the substudy has also been published in a peer-reviewed journal is not stated on the listing [1].
Why it matters for patients
Muscle-loss headlines about GLP-1 medications are often compared as if they were measured the same way. They are not. The STEP UP substudy suggests that an MRI-based analysis can report a smaller lean-tissue share of weight loss than a DXA-based analysis of the same drug [1]. If you read one number in one story and a different number in another, the method behind each figure is part of the explanation.
The distinction matters because lean tissue includes muscle, which affects strength and everyday function. The posting does not break the substudy results down by age or by any other group, so it does not show who lost more or less lean tissue [1]. Whether a given person's risk differs based on age, weight, other conditions or how long they take the drug is not addressed in the material posted [1].
It is also worth keeping the scope in view: this is a substudy of one trial, reported at a medical meeting, not the full STEP UP results. The posting does not include the trial's main weight-loss findings, its full safety data, or a comparison with any other drug [1].
What happens next
The listing page shows Novo Nordisk's upcoming congress schedule, but it does not give a date for peer-reviewed publication of the STEP UP body-composition substudy or for the full STEP UP results [1]. Whether the 7.2 mg dose moves forward with US regulators has not been disclosed [1]. Until full data and the specific percentages are reported, the size of the gap between the MRI and DXA results in this substudy remains unknown [1].
Sources
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