THE MUSCLE LOSS PROBLEM
Let's be direct: rapid weight loss always involves some muscle loss. With GLP-1s alone, roughly 25-40% of weight lost is lean mass. That's not great — especially for men who've worked hard to build muscle.
This isn't unique to GLP-1s. It happens with any rapid weight loss, including bariatric surgery and aggressive dieting. Your body, in caloric deficit, will break down some muscle for energy. The question is: can we minimize it?
The BELIEVE trial provides the most compelling evidence yet that yes, dramatically so.
THE BELIEVE TRIAL RESULTS
Presented at ObesityWeek 2024, the BELIEVE trial enrolled 507 participants for 72 weeks. The study compared three groups: semaglutide alone, bimagrumab alone, and the combination of both.
| Group | Total Weight Loss | % From Fat | Muscle Preserved |
|---|---|---|---|
| Semaglutide alone | 16.0% | 71.8% | Baseline |
| Bimagrumab alone | Minimal | — | Maintained |
| Combination | 22.1% | 92.8% | +67% vs semaglutide alone |
The combination achieved more total weight loss (22.1% vs 16.0%) while preserving significantly more muscle (92.8% fat ratio vs 71.8%). That's 67% better muscle preservation.
WHAT IS BIMAGRUMAB?
Bimagrumab is a monoclonal antibody that blocks the myostatin/activin pathway. Myostatin is your body's natural "muscle brake" — it limits how much muscle you can build and signals muscle breakdown during caloric deficit.
By blocking myostatin, bimagrumab essentially tells your body: "keep the muscle, just burn the fat." It was originally developed for conditions like sarcopenia (age-related muscle loss) and muscular dystrophy.
🔬 Availability Note
Bimagrumab is NOT currently FDA-approved or commercially available. It's in clinical development. The BELIEVE trial establishes proof-of-concept that muscle loss during GLP-1 treatment can be dramatically reduced — but you can't get bimagrumab prescribed today.
WHAT THIS MEANS FOR MEN NOW
While we wait for combination therapies like semaglutide + bimagrumab to reach the market (likely 2-3+ years), there are evidence-based strategies you can implement today to improve your muscle preservation ratio.
💪 Muscle Preservation Protocol
THE FUTURE OF GLP-1 COMBINATIONS
BELIEVE isn't the only combination being studied. The pipeline includes:
- Semaglutide + bimagrumab — BELIEVE trial (covered here)
- Retatrutide — Triple agonist (GLP-1/GIP/glucagon) showing 28.7% weight loss with potentially better body composition
- CagriSema — Semaglutide + cagrilintide, amylin analog that may improve fat:lean ratio
The trajectory is clear: next-generation treatments will increasingly address the muscle loss limitation. The question for men today is how to optimize results with available options while better solutions enter the market.
REALISTIC EXPECTATIONS
Even with optimal protein and training, you'll likely lose some muscle during rapid weight loss. The goal is to minimize it, not eliminate it entirely. Based on current data:
- GLP-1 alone, no intervention: ~25-40% of loss is lean mass
- GLP-1 + protein + resistance training: Estimated ~15-25% lean mass (based on exercise physiology principles, not direct trials)
- GLP-1 + bimagrumab: ~7% lean mass (BELIEVE trial)
The difference between 40% muscle loss and 15% muscle loss is enormous for long-term metabolic health and physical function. It's worth the effort.
READY TO START?
Compare telehealth providers offering GLP-1 prescriptions for men.
Compare Providers →📚 Sources
[1] BELIEVE Trial. ObesityWeek 2024. "Semaglutide plus Bimagrumab in Obesity: Body Composition Outcomes."
[2] Heymsfield SB, et al. "Mechanisms, Pathophysiology, and Management of Obesity-Related Muscle Loss." NEJM. 2024.
[3] Morton RW, et al. "A systematic review of the effects of resistance training on body composition." Br J Sports Med. 2018.