Could a New Drug Help Prevent Muscle Loss During GLP-1 Weight Loss?
GLP-1–based medications such as semaglutide and tirzepatide have transformed medical weight management. However, researchers are increasingly focused on an important question: How can patients lose fat while preserving as much muscle as possible?
Weight loss—whether achieved through diet, surgery, or medication—typically includes some loss of lean body mass. Clinical research suggests that approximately 25% to 40% of the weight lost with incretin-based therapies may come from lean tissue. Lean body mass includes skeletal muscle, but it also includes organs, connective tissue, and body water, so it should not be interpreted as muscle alone.
Maintaining skeletal muscle is especially important as we age because muscle supports strength, mobility, insulin sensitivity, metabolic health, and long-term independence.
A New Drug Called Apitegromab
One of the newest investigational treatments is apitegromab, a monoclonal antibody that selectively inhibits the activation of myostatin.
Myostatin is a naturally occurring protein that limits muscle growth. By reducing myostatin activity, researchers hope apitegromab can help preserve muscle while patients lose weight with medications such as tirzepatide.
In the 2026 Phase 2 EMBRAZE trial, 102 adults with overweight or obesity received either:
Tirzepatide plus apitegromab
Tirzepatide plus placebo
After 24 weeks, the patients receiving apitegromab lost approximately 1.9 kilograms—or 4.2 pounds—less lean mass than those receiving tirzepatide alone. This represented approximately 55% better lean-mass preservation.
Total weight loss was similar between the groups. However, lean mass accounted for approximately 14.6% of the weight lost with apitegromab compared with 30.2% in the control group.
Adverse-event rates were also similar between the two groups, although this was a small and relatively short trial. The study did not demonstrate a meaningful difference in physical-function measurements, and additional research is needed to determine whether preserving DEXA-measured lean mass translates into greater strength or improved long-term outcomes.
Read the apitegromab study in Nature Medicine (https://www.nature.com/articles/s41591-026-04440-4)
Bimagrumab May Also Improve the Quality of Weight Loss
Another promising investigational medication is bimagrumab, an antibody that blocks activin type II receptors involved in regulating muscle and fat tissue.
In the 507-participant Phase 2 BELIEVE trial, researchers evaluated bimagrumab, semaglutide, and combinations of the two medications.
The high-dose combination produced approximately 22.1% body-weight reduction at 72 weeks while largely preserving lean mass. Researchers also observed greater fat loss than with semaglutide alone.
Common adverse effects associated with bimagrumab included muscle spasms, diarrhea, and acne. The trial also did not demonstrate a significant improvement in grip strength or patient-reported physical function.
Read the bimagrumab study in Nature Medicine (https://www.nature.com/articles/s41591-026-04204-0)
Are These Medications Available Now?
No. Neither apitegromab nor bimagrumab is currently approved as a treatment for muscle loss associated with GLP-1 therapy.
These results are promising, but larger and longer clinical trials are still needed to answer several important questions:
Does preserving lean mass also preserve strength and physical function?
Which patients are most likely to benefit?
What are the long-term risks of altering myostatin or activin signaling?
Will these medications be safe and practical for routine obesity treatment?
Can the benefits be maintained after treatment stops?
Patients should be cautious of clinics or online sellers claiming to offer these investigational drugs before regulatory approval.
Protecting Muscle During GLP-1 Treatment Today
While researchers develop new medications, the current foundation of muscle preservation remains:
Progressive resistance training
Adequate dietary protein
Avoiding unnecessarily rapid weight loss
Maintaining sufficient calorie and nutrient intake
Monitoring strength and physical performance
Individualizing the GLP-1 dose to the patient’s needs
Evaluating hormone, thyroid, nutritional, and other medical factors when appropriate
A DEXA scan can help track body composition, but the number should be interpreted alongside strength, physical function, diet, training, and overall health.
The Future of Medical Weight Management
The next generation of obesity treatment may focus on more than the number on the scale. The goal will increasingly be to improve the quality of weight loss—maximizing fat reduction while preserving muscle, strength, and metabolic health.
Apitegromab and bimagrumab represent two of the most promising drugs currently being studied for this purpose. Their early results are encouraging, but they remain investigational and are not yet ready for routine clinical use.
At Morrell Wellness, we follow emerging research closely while focusing on safe, individualized, evidence-informed weight management. If you are using a GLP-1 medication or are concerned about losing muscle during weight loss, schedule a consultation to discuss a plan designed around your health, body composition, and long-term goals.
This article is for educational purposes only and does not replace individualized medical advice. Investigational medications discussed in this article are not approved for the prevention of GLP-1–associated muscle loss.
