Semaglutide Muscle Loss: The Drugs Being Tested to Protect Muscle

You've been on semaglutide for a few months, the scale is finally moving, and yet the stairs at home feel harder than they did last spring. At the gym, the weights you used to handle easily now feel heavy. That mix of progress and weakness is why many people ask whether semaglutide muscle loss can be managed, and what the research says about it.

This post covers the wider research pipeline, not a single molecule. Some of these approaches are at early stages, and none of them is approved for muscle preservation with semaglutide today. If you want background on one candidate, our earlier trevogrumab post goes through that drug's trial data. This post looks at what else is in development and how to read the news around it.

Why muscle goes down along with fat

Any calorie deficit reduces body weight, and that weight comes from both fat and lean tissue. Heymsfield and Wadden's 2017 review in the New England Journal of Medicine describes how obesity and its treatment affect body composition, including the lean tissue lost alongside fat during caloric restriction.

It helps to separate three numbers. Total weight is what the scale shows. Fat mass is the adipose tissue you carry. Lean mass includes muscle, bone, organs, and water. A DXA scan (dual-energy X-ray absorptiometry) estimates fat and lean mass separately by passing two X-ray energy levels through the body. Cheaper tools exist, but they are less precise.

The STEP program was the phase 3 series that tested semaglutide 2.4 mg, and the STEP 1 results were published in the New England Journal of Medicine. Body composition was also examined in a DXA substudy, which found that lean tissue made up part of the weight lost. Check the original publications for the exact figures before you quote any percentage, because those numbers are easy to misremember.

Appetite is another piece of the puzzle. Semaglutide often reduces hunger, and eating less can mean eating less protein. Lower protein intake during weight loss is a plausible reason lean mass might fall faster, but researchers are still testing whether it is the main driver. Treat it as a working hypothesis, not a settled answer.

The myostatin and activin drugs in development

Myostatin and activin receptor signaling act as brakes on muscle growth. Several candidates try to block those brakes so that muscle holds on while fat comes off. The open question is whether that helps real-world function, not just scan numbers.

Bimagrumab (Eli Lilly)

Bimagrumab is an antibody that targets the activin receptor type II. Lilly has tested it in phase 2 studies combined with incretin medicines, including tirzepatide. Its results have been shared at medical meetings, so check the registry entry and the conference abstract for the venue and year. Whether combination data with semaglutide exist is something to confirm there too.

Trevogrumab with garetosmab (Regeneron)

Regeneron is testing trevogrumab together with garetosmab, which targets a related signaling molecule. We covered the trial details in our earlier post, so we won't repeat them here.

For each candidate, the registry entry gives you the key facts you need to compare:

• Trial phase, such as phase 2 or phase 3
• Population, such as adults with obesity, with or without type 2 diabetes
• Primary endpoint, whether body composition or physical function
• Current status, such as recruiting, active, or completed

Company press releases can add context, but treat them as company statements rather than peer-reviewed findings.

Other approaches still at earlier stages

Enobosarm, from Veru, is a selective androgen receptor modulator that has been tested for lean mass preservation during weight loss. Its phase 2 design, sample size, and reported safety signals are listed in the trial registry. Because this drug class can affect the liver and cardiovascular system, trials of this kind monitor those organs closely, and you should read the safety section carefully.

Some programs get paused or redesigned. The reasons vary, from funding and dose choices to unclear endpoints. You won't always find that in headlines. Look at company pipeline updates and changes in registry status, such as "active, not recruiting" or "terminated," to see what actually happened.

Many muscle-targeted drugs were first developed for sarcopenia, cachexia, or muscular dystrophy. Moving them into obesity raises separate safety questions, because the people involved often have different metabolic and cardiovascular profiles, and long-term data are still limited.

A phase 2 result can show early signals on body composition and short-term safety. It cannot tell you whether a drug prevents falls, keeps strength steady for years, or protects independence. Those outcomes need longer, larger studies that measure function directly.

What helps today, based on existing evidence

Resistance training is the strongest tool most people already have. The WHO's 2020 guidelines recommend that adults do muscle-strengthening activities at moderate or greater intensity, involving all major muscle groups, on two or more days a week. Weights, resistance bands, and bodyweight squats all count, so start where you are and build up.

Protein is the other piece. The International Society of Sports Nutrition position stand suggests 1.4 to 2.0 grams of protein per kilogram of body weight per day for physically active adults. Your own target may differ, so talk it over with your clinician. When appetite is low, try eggs, Greek yogurt, cottage cheese, lentils, tofu, fish, or chicken. Eat smaller meals more often and eat protein first. OzemNews publishes our weekly GLP-1 roundup, where we follow new studies on protein, exercise, and muscle as they come out.

These habits support muscle, but they do not replace medical advice about dosing or side effects.

Access, regulation, and what to watch out for in Brazil

No muscle-preserving add-on for semaglutide holds an ANVISA approval for that use. Before you accept that, check the ANVISA database and the current bulário for any product you're considering.

Avoid unregistered products and compounded mixtures that promise muscle gains. ANVISA has issued alerts about unregistered GLP-1 products, and the latest notice is the best place to see which products are flagged.

To see whether a trial is recruiting in Brazil, open ClinicalTrials.gov, filter by country, and then filter by recruitment status. If you want to keep up with regulatory updates, OzemNews covers them in the regulatory coverage on our site.

Practical questions for your doctor and how to track muscle

At your next appointment, ask four concrete questions:

• Has my body composition been measured, and if so, with which method?
• Which tools are available here: DXA, bioimpedance, or neither?
• How should I track grip strength or a sit-to-stand test, and how often?
• At what level of lean mass loss would you change my plan?

Home bioimpedance scales are convenient, but readings shift with hydration, meals, and the time of day. Use them to spot trends over weeks, not to judge a single number.

For four to eight weeks, record your strength workouts, including exercises, loads, and reps, along with your daily protein intake. That gives your doctor real data to review. The OzemNews team also publishes guides for people on GLP-1 treatment that explain which tracking tools are reliable and which ones are mostly noise.

What to watch next and how to read new headlines

Some upcoming data will matter more than others. Phase 3 start announcements show that a candidate has moved forward. Longer follow-up periods reveal whether gains last. Results that report function, such as strength or gait speed, tell you more than scan numbers alone.

When a headline says "muscle saved," look for the underlying numbers. A lean mass percentage can sound impressive while the absolute loss in kilograms stays small, or it can hide a large drop in total weight. Ask how many kilograms were involved, what the comparison group did, and whether strength or walking speed changed.

Research on protecting muscle during semaglutide treatment is promising in parts and incomplete in others. These approaches may help someday, but none is a guaranteed fix. The choices you make now should rest on what is proven today and on a conversation with your healthcare team.

FAQ

Can I take a muscle-protecting drug along with semaglutide today?

No muscle-preserving add-on for semaglutide is approved for that use in Brazil right now. Ask your doctor about what is available and what is still in trials.

Does protein alone prevent muscle loss on semaglutide?

Protein supports muscle, especially when combined with resistance training. It may help, but it does not guarantee that you will keep all your lean mass.

Is home bioimpedance accurate enough to track muscle?

Home devices work best for spotting trends over time. Hydration and meal timing can change the readings, so single numbers can mislead you.

How can I find muscle-related trials recruiting in Brazil?

Use ClinicalTrials.gov, filter by country and recruitment status, and then read each entry for its phase, population, and primary endpoint.

Sources

• Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1), New England Journal of Medicine
• Heymsfield SB, Wadden TA. Mechanisms, Pathophysiology, and Management of Obesity, New England Journal of Medicine
• WHO Guidelines on Physical Activity and Sedentary Behaviour (2020)
• Jäger R et al. International Society of Sports Nutrition Position Stand: Protein and Exercise, Journal of the International Society of Sports Nutrition
• ClinicalTrials.gov, U.S. National Library of Medicine trial registry
• ANVISA, Agência Nacional de Vigilância Sanitária (alerts and product database)