Bimagrumab: The Drug That Melts Fat and Keeps the Muscle

Everyone is talking about GLP1’s and 2’s and 3’s....but there is a drug that seems to be way more efficient....

By Valérie Orsoni — Biohacker & Longevity Expert
Valérie Orsoni is a biohacker, author of 56 books, and founder of biohacker.fr. She has been tracking her biology through N=1 self-experimentation protocols since 1998. She has completed a Stanford Genetics Longevity Research certificate, two Stanford Medicine certificate programs: Nutrition Science and GLP-1s & weight loss. She is currently enrolled in a Stanford Geneticas & AI certification program. She was named in the Top 50 Longevity Leaders by Life Spanning magazine and is currently the #1 on the Longevity Cup Leaderboard (chronological age -23 years).

The muscle problem nobody wanted to talk about

I have been biohacking since 1998, and if there is one thing 28 years of experiments on myself have taught me, it is this: muscle is the hardest asset to build and the easiest to lose.

I recently proved it the painful way. To test the yoga and Pilates crowd who swear you do not need weights, I stopped lifting for 12 weeks. I kept running, kept everything else in my protocol. My DEXA scan was brutal: 2 kg of muscle gone and 1.5% more body fat. When I walked back into the gym on October 15, my deadlift had dropped from 140 lb to about 80 lb.

So when I read about a drug that claims to strip fat while protecting muscle, I do not read it as a curious scientist. I read it as someone who has just watched her own muscle disappear on a scan.

GLP-1 drugs work. They also take muscle with the fat, and for anyone who cares about longevity, that is the part that should keep you up at night.

In the BELIEVE trial, published in Nature Medicine in March 2026, about 28% of the weight lost on semaglutide alone came from lean mass. Add bimagrumab, and fat accounted for 92.8% of the weight lost. Lean mass loss dropped from 7.4% to 2.9%.

Muscle is not vanity. It is your glucose sink, your metabolic reserve, your fall insurance, and one of the strongest predictors of how long and how well you live. A drug that strips fat while sparing it changes the conversation. So let’s look at what bimagrumab actually is, what the data shows, and what it does not show yet.

Let’s do a deep dive together and see if bimagrumab is for you.