How do weight loss drugs and bariatric surgery impact your body fat percentage?

Embargoed until: Publicly released: 2026-01-10 03:00

International

Photo by Towfiqu barbhuiya on Unsplash. Story by Rachel McDonald, Australian Science Media Centre

Bariatric surgery and GLP-1 RA weight loss drugs semaglutide and tirzepatide can improve body fat percentage as well as assisting overall weight loss, according to international research. The researchers say evidence supports these weight loss options for reducing BMI, but it is important to understand how much weight lost is body fat, as losing too much fat-free body mass can increase some health risks. They recruited 1,257 bariatric surgery patients and 1,809 people taking semaglutide or tirzepatide for two years, measuring changes in overall weight loss and body fat percentage. The researchers say both surgery and the drugs were linked to substantial body fat loss, moderate fat-free mass loss and improved body fat percentage, with all three changes more strongly apparent for the surgery patients.

News release

From: JAMA

Body Composition Changes After Bariatric Surgery or Treatment With GLP-1 Receptor Agonists

About The Study: In this single-center cohort study, both bariatric surgery and semaglutide or tirzepatide treatment were associated with substantial fat mass loss, moderate fat-free mass (FFM) loss, and improved FFM to fat mass ratio. These findings provide evidence to guide interventions aimed at preserving FFM while promoting fat loss.

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Research JAMA, Web page The URL will go live after the embargo ends

Journal/
conference: JAMA Network Open

Research:Paper

Organisation/s: Vanderbilt University Medical Center, USA

Funder: Dr Yu is supported by grants R01DK126721 and R01CA275864 from the National Institutes of Health. The Vanderbilt Institute for Clinical and Translational Research is funded by the National Center for Advancing Translational Sciences Clinical Translational Science Award Program, Award Number 5UL1TR002243.

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