GLP-1 Muscle Loss in 2026: What Regeneron's New Trevogrumab Results Mean for Your Weight Loss Plan

COURAGE enrolled nearly 1,000 adults aged 18 to 65 with obesity and followed them for 52 weeks. Everyone received semaglutide 2.4 mg — the same dose used in Wegovy — and participants were randomized to add trevogrumab at several doses, trevogrumab plus a second antibody called garetosmab, or placebo.

The headline numbers, from Regeneron's full results announcement:

At 26 weeks, patients on semaglutide plus placebo lost 6.7% of their lean mass by DXA scan. Adding trevogrumab 75 mg cut that to 3.3% — roughly half the loss. The lower 25 mg dose landed in between, at 4.7%. By 52 weeks the pattern held: 7.3% lean mass loss on semaglutide alone versus 4.2% with trevogrumab 75 mg.

MRI imaging of thigh muscle told an even stronger story: trevogrumab preserved roughly 70% of the thigh muscle that would otherwise have been lost with semaglutide alone at 52 weeks, according to the trial data published by Regeneron. DXA measures all lean tissue, which includes water and organs; MRI looks directly at skeletal muscle, which is the tissue that actually drives strength and metabolism.

Separate data presented at EASD also suggested the antibody helped patients regain muscle after stopping GLP-1 therapy — relevant for the many patients who discontinue treatment and worry about rebound in a worse body composition than where they started.

When you lose weight by any method — diet, surgery, or medication — some of it comes from lean tissue. On GLP-1 medications, roughly 30% of total weight lost can be lean mass, a figure widely cited in the reporting on this trial.

That matters for three reasons. First, muscle is metabolically active: losing it lowers the number of calories you burn at rest, which can make maintenance harder after you reach your goal. Second, strength and mobility depend on it, especially for patients in their 50s and 60s, where age-related muscle loss is already underway. Third, if you ever stop the medication and regain weight, the regain tends to be mostly fat — so each cycle can leave body composition worse.

This is why Regeneron's next step is a trial of trevogrumab specifically in older adults with obesity and reduced muscle mass and strength, the group with the most to lose from sarcopenia.

Trevogrumab plus semaglutide looked reassuringly similar to semaglutide alone in this trial. Adverse events occurred in 77% of trevogrumab patients versus 82% on placebo, and the most common issues — nausea, constipation, diarrhea, and vomiting — are the familiar GLP-1 side effects rather than anything new from the antibody.

The important caveat sits in the arms that combined trevogrumab with the second antibody, garetosmab: two deaths occurred during the first 26 weeks in higher-dose combination groups, one from cardiac arrest and one of undetermined cause. The clean result belongs to trevogrumab alone on top of semaglutide; the three-drug combination carries open safety questions that will need to be resolved before it goes further.

As always, these are trial-level statistics, not a personal guarantee. Any weight loss medication decision should be made with a licensed provider who knows your history, particularly your cardiac and thyroid history and any medications you already take.

Not soon — and it is important to be realistic about that. COURAGE is a Phase 2 trial. Trevogrumab still needs larger Phase 3 studies and FDA review before it could be prescribed, a process that typically takes years. Analysts told Reuters the market for muscle-preserving add-ons could reach $30 billion a year by 2035, and Lilly and other companies are racing to develop similar drugs — but none of them is available to patients today.

What the data does change today is the conversation. It confirms with hard numbers that lean mass loss on GLP-1s is real, measurable, and large enough to be worth actively managing — not a reason to avoid treatment, but a reason to treat thoughtfully.

You do not need to wait for a new drug to act on this. The fundamentals are available to every patient today:

Prioritize protein. Reduced appetite makes it easy to under-eat protein. Most clinicians advising GLP-1 patients suggest anchoring each meal around a protein source, since protein supplies the raw material for maintaining muscle during a calorie deficit.

Add resistance training. Two to three sessions a week of strength work — even bodyweight or band exercises at home — signals your body to hold onto muscle while fat comes off. Cardio alone does not provide the same protection.

Titrate at a pace you can eat through. If nausea is suppressing your food intake to the point you cannot meet protein targets, tell your provider. Slower dose escalation or anti-nausea support can keep treatment sustainable, and JoeyMed's providers routinely adjust plans for exactly this reason.

Track more than the scale. Progress photos, strength benchmarks, and how clothes fit capture fat-versus-muscle changes the scale hides.

If you are considering GLP-1 treatment — or you are already on semaglutide or tirzepatide and want a plan that protects your strength while the weight comes off — JoeyMed can help. Our licensed providers evaluate your health history online, determine whether treatment options like high-dose tirzepatide are appropriate for you, and build in the protein, training, and side-effect management guidance that this week's data shows really matters. Visit our weight loss program to complete a free online assessment, or explore our wellness and longevity services if maintaining strength and healthy aging are your bigger goals.

The future of weight loss is shifting from pounds lost to health gained. The good news from COURAGE is that medicine is catching up to what patients have wanted all along: losing the fat, and keeping the strength.