In just a few years, weight-loss medicine has shifted from dubious “miracle” fixes to genuinely transformative treatments, with GLP-1 agonists such as Mounjaro and Wegovy already helping millions curb appetite.
As researchers learn more about how these drugs work in the body, interest has grown in using semaglutide-based therapies beyond basic weight management—and large, well-funded studies are now testing how to refine them and improve results.
A new paper released this week by scientists linked to several pharmaceutical companies, including Eli Lilly (the maker of Mounjaro), points to a potential new direction in the field that some are informally calling “musclezempic.”
The idea is straightforward: pair GLP-1 medications with a separate treatment designed to preserve or build muscle. The researchers reported that this combination may drive greater overall weight and fat loss while also reducing a common downside seen with significant weight reduction.
When people lose a substantial amount of weight, they typically reduce body fat—which is the goal—but they can also lose some lean mass, including muscle. That isn’t unique to GLP-1 drugs; it’s a frequent feature of rapid or major weight-loss of many kinds.
Even so, because fat often drops more dramatically than muscle, many people still end up with a better lean-to-fat balance after weight loss. The Nature study published this week suggests that pairing semaglutide with a drug called bimagrumab may improve that ratio further.
Participants who used bimagrumab alongside semaglutide also showed greater overall weight loss than those taking GLP-1 therapy alone.
The researchers said: “These findings support further development of bimagrumab, alone or in combination with incretin therapy, to achieve optimal weight loss.”
If the approach holds up in further trials, it could be especially helpful for people with obesity who find exercise difficult at higher body weights, potentially helping them regain strength and function sooner while they continue to lose weight.
So what exactly is bimagrumab? It’s not a medication most people would recognize or have been offered through routine care.
Bimagrumab is an experimental treatment being explored for conditions involving muscle loss. Eli Lilly has acquired the drug as research continues into how it might work alongside established weight-loss medications.
Scientifically, it’s a human monoclonal antibody—a lab-made antibody derived from a single immune cell line.
In treatment, the antibody blocks a receptor involved in regulating muscle growth, essentially removing a biological brake that can limit muscle gain.
In the Nature study, patients receiving higher doses of both bimagrumab and semaglutide saw larger drops in body weight after 48 weeks: about 20 percent, compared with 15 percent among those receiving only higher-dose semaglutide.
The gap widened later in the study. By week 72, the combination group had lost an average 45.7 percent of their fat mass, versus 27.8 percent in the group receiving only GLP-1 medication.
Still, while the results have fueled talk of a future “musclezempic” option, this combination remains in Phase II trials.
That means it could be some time before a widely available treatment can reliably support major weight loss while also helping patients maintain—or even add—muscle.