The short answer
Adding experimental bimagrumab to semaglutide produced greater average weight reduction and less loss of lean tissue. That does not automatically mean better strength.
What was tested?
BELIEVE randomized 507 adults without diabetes across nine groups, testing bimagrumab, semaglutide, combinations and placebo. Treatment lasted 48 weeks; semaglutide treatment was open-label.
Kilograms lost
Original visual based on the study.
| Group or measure | Result |
|---|---|
| Bimagrumab 30 mg/kg plus semaglutide 2.4 mg | 17.8 kg |
| Semaglutide 2.4 mg | 14.2 kg |
| Bimagrumab 30 mg/kg | 9.3 kg |
| Placebo | 3.3 kg |
What changed?
Treatment-regimen estimates of weight loss at week 48 were:
Bimagrumab 30 mg/kg plus semaglutide 2.4 mg: 17.8 kg.
Semaglutide 2.4 mg: 14.2 kg.
Bimagrumab 30 mg/kg: 9.3 kg.
Placebo: 3.3 kg.
Combination groups lost less DXA-measured lean tissue than semaglutide groups. Lean tissue includes more than skeletal muscle. The trial did not establish a consistent functional advantage.
What were the trade-offs?
Bimagrumab adverse events included muscle spasms, diarrhoea and acne; semaglutide commonly caused digestive symptoms. Multiple comparisons were not statistically adjusted, limiting definitive conclusions. The later extension was open-label.
The useful takeaway
Body composition deserves attention alongside weight. These findings support further study, not a recommendation to add an experimental treatment.
Sources
Heymsfield and colleagues, Nature Medicine, 2026. Funded by Lilly and, before acquisition, Versanis Bio.