Weight Loss Drugs That Preserve Muscle: What to Know

One of the biggest concerns with rapid weight loss is losing muscle along with fat, and a new wave of drugs aims to fix that by preserving or even building lean mass while cutting fat. The leader is bimagrumab, an antibody that increases muscle, and several other approaches are in development. All of these are investigational. Here’s how muscle-preserving drugs work, which ones are furthest along, and what protects muscle right now while they mature.

Why Muscle Loss Is a Concern

Any significant weight loss (from dieting, surgery, or GLP-1 drugs) typically includes losing some muscle along with fat. Research suggests roughly a third of the weight lost on GLP-1 drugs can come from lean mass. That matters because muscle supports metabolism, strength, and physical function, and losing too much can be especially problematic for older adults or anyone at risk of frailty. As GLP-1 drugs drive larger, faster weight loss than ever, this “quality of weight loss” question has become a major focus.

How Muscle-Preserving Drugs Work

These drugs don’t reduce appetite like GLP-1s. Instead, they act on muscle and fat tissue directly, generally by blocking signals that normally limit muscle growth. A review published in the journal Obesity and Endocrinology in 2026 examined this emerging category, describing how these agents are being combined with GLP-1 drugs to shift weight loss toward fat and away from muscle. The idea is a two-drug approach: the GLP-1 drug drives weight loss, and the muscle-preserving drug shapes what kind of weight is lost.

The Leading Candidates

Here’s a look at the main muscle-preserving approaches in development.

Bimagrumab: The Frontrunner

Bimagrumab is the most developed. It’s a monoclonal antibody that blocks activin receptors, which normally restrain muscle growth, so it increases muscle while reducing fat. In a phase 2 trial combining bimagrumab with semaglutide, the combination produced substantial weight loss with the vast majority coming from fat, and bimagrumab on its own actually increased lean muscle mass. That’s a striking result: not just preserving muscle, but building it while cutting fat. Consider a hypothetical older patient worried that aggressive weight loss will leave them weaker: a drug that maintains or builds muscle addresses exactly that fear.

Other Approaches

Beyond bimagrumab, several drugmakers are testing muscle-preserving antibodies (like trevogrumab, sometimes combined with a second antibody) alongside GLP-1 drugs, and a selective androgen receptor modulator (enobosarm) is also being studied. It’s an active area, reflecting how seriously the field is taking muscle preservation. It’s also worth noting that some newer weight-loss drugs are being designed to preserve muscle better on their own, so the concern is being addressed from multiple directions.

What Protects Muscle Right Now

Here’s the practical part: you don’t need an investigational drug to protect muscle during weight loss. Two proven, available strategies do a lot: resistance training (lifting weights or bodyweight exercises) signals your body to keep muscle, and adequate protein intake provides the building blocks. Anyone losing weight on a GLP-1 drug can use both today. These aren’t as dramatic as a muscle-building antibody, but they’re effective, free, and available now.

What This Means for You Right Now

The muscle-preserving drugs described here are all investigational, and TrimRx does not offer them. TrimRx provides currently available weight-loss options, including compounded semaglutide and compounded tirzepatide plus brand GLP-1 injectables. If you’re losing weight and want to protect muscle now, resistance training and sufficient protein are the proven tools, and a provider can help you build weight loss and muscle preservation into one plan.

Frequently Asked Questions

Do weight-loss drugs make you lose muscle?

Some muscle loss is typical with any significant weight loss, and research suggests roughly a third of weight lost on GLP-1 drugs can come from lean mass. This is why muscle-preserving drugs and strategies are getting attention, though the effect varies by person.

Which drug best preserves muscle?

Bimagrumab is the furthest along and stands out because it can actually increase muscle while reducing fat. Other antibodies (like trevogrumab) and a selective androgen receptor modulator (enobosarm) are also in development. All are investigational, so none is available yet.

How can I keep muscle while losing weight now?

Resistance training and adequate protein intake are the proven, available strategies. Lifting weights or doing bodyweight exercises signals your body to preserve muscle, and protein provides the building blocks. Both can be used alongside any weight-loss treatment today.

To build a plan that fits you, you can explore the options available to you now with a licensed provider.

This information is for educational purposes and is not medical advice. The muscle-preserving drugs referenced are investigational and not FDA approved; details and timelines may change. Consult a healthcare provider before starting any medication or exercise program. Individual results may vary.