Semaglutide Causes Significant Fat Loss but Also Reduces Lean Muscle Mass | Research

The takeaway

The SEMALEAN study found semaglutide 2.4mg produced substantial fat loss in obesity patients, but also significant lean mass reduction, with preserved handgrip strength at 12 months.

115 patients, 12-month DXA data
Prospective body composition tracking during semaglutide 2.4mg treatment

What the researchers found

Semaglutide 2.4mg produced significant weight and fat loss but also reduced lean body mass, while handgrip strength was generally preserved through 12 months.

Why it matters

The lean mass loss debate is one of the biggest concerns with GLP-1 medications. This study provides objective DXA-measured data showing the actual body composition changes during semaglutide treatment.

How the study worked

Prospective observational study with 115 patients; body composition measured by DXA, muscle function by handgrip strength, and resting energy expenditure tracked at baseline, 7 months, and 12 months.

What this study cannot tell us

No control group; prospective but observational design; handgrip strength is a limited measure of overall muscle function.

How to read the evidence

Prospective observational study — provides objective body composition data but lacks a randomized control group.

When this study was published

Published 2026 in Diabetes, Obesity & Metabolism. Data from February 2022 to November 2024.

The bigger picture

As millions use GLP-1 medications for weight loss, understanding the ratio of fat-to-lean mass loss is critical for long-term health, especially in older adults at risk for sarcopenia.

Questions still open

Can resistance exercise preserve lean mass during semaglutide treatment?
Does the lean mass loss lead to functional impairment in older or frailer patients?

Common questions

Does semaglutide make you lose muscle along with fat?

Yes, this study found semaglutide causes some lean mass loss alongside fat loss, though muscle strength (measured by handgrip) was generally maintained through 12 months of treatment.

How was body composition measured in this study?

Researchers used DXA scans, considered the gold standard for measuring fat mass, lean mass, and bone density, at baseline, 7 months, and 12 months.

Read the original research

Impact of Semaglutide on fat mass, lean mass and muscle function in patients with obesity: The SEMALEAN study.

Diabetes, obesity & metabolism, 28(1), 112-121

View on PubMed ↗Publisher’s paper ↗

Citation

Alissou, Mathieu; Demangeat, Thomas; Folope, Vanessa; Van Elslande, Hélène; Lelandais, Hélène; Blanchemaison, Julia; Cailleaux, Pierre-Emmanuel; Guney, Suzan; Aupetit, Alexandra; Aubourg, Agnès; Rapp, Clément; Petit, André; Godin, Morgane; Vignal, Luc; Grigioni, Sébastien; Déchelotte, Pierre; Colange, Guillaume; Coëffier, Moïse; Achamrah, Najate. (2026). Impact of Semaglutide on fat mass, lean mass and muscle function in patients with obesity: The SEMALEAN study.. Diabetes, obesity & metabolism, 28(1), 112-121. https://doi.org/10.1111/dom.70141