Can we lose fat without losing muscle on weight-loss drugs?
GDF8 and activin A blockade protects against GLP-1–induced muscle loss while enhancing fat loss in obese male mice and non-human primates
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Dual blockade of GDF8 and activin A alone (without semaglutide) improved body composition in mice and primates—even without appetite suppression.
Most people assume muscle growth or fat loss requires calorie restriction or drugs like semaglutide. But blocking just these two proteins improved fat loss and muscle gain on its own—suggesting they’re master regulators of body composition.
Practical Takeaways
If you're on or considering GLP-1 drugs like semaglutide, prioritize resistance training and high-protein intake to minimize muscle loss—until targeted therapies like GDF8/activin A blockers become available.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Dual blockade of GDF8 and activin A alone (without semaglutide) improved body composition in mice and primates—even without appetite suppression.
Most people assume muscle growth or fat loss requires calorie restriction or drugs like semaglutide. But blocking just these two proteins improved fat loss and muscle gain on its own—suggesting they’re master regulators of body composition.
Practical Takeaways
If you're on or considering GLP-1 drugs like semaglutide, prioritize resistance training and high-protein intake to minimize muscle loss—until targeted therapies like GDF8/activin A blockers become available.
Publication
Journal
Nature Communications
Year
2025
Authors
Jason W. Mastaitis, Daniel Gomez, J. Raya, Diana Li, Soo Min, Michael Stec, Sandra Kleiner, Toya McWilliams, Judith Y. Altarejos, Andrew J. Murphy, G. Yancopoulos, Mark W. Sleeman
Related Content
Claims (5)
To lose body fat, you must consume fewer calories than you expend, and the size of this calorie deficit has a greater impact on fat loss than whether you do running, weightlifting, or other forms of exercise.
In obese male primates, combining a drug that blocks two specific muscle-regulating proteins with semaglutide leads to greater increases in muscle mass and more fat loss than semaglutide alone, along with improved blood sugar and cholesterol levels after 20 weeks of treatment.
In obese male primates, combining a treatment that blocks two specific proteins (GDF8 and activin A) with GLP-1 therapy leads to larger improvements in blood sugar control and cholesterol levels than GLP-1 therapy by itself.
In obese male mice and non-human primates, blocking two specific proteins (GDF8 and activin A) while using a GLP-1 receptor agonist helps maintain or increase muscle mass and enhances fat loss, leading to better body composition and improved metabolic indicators like lower liver fat and healthier blood lipids.
In obese male mice, combining semaglutide with a treatment that blocks GDF8 and activin A leads to about twice as much fat loss over four weeks compared to semaglutide alone, even when total weight loss is the same, indicating that preserving muscle may help the body remove more fat.