How to Stop Muscle Loss on a GLP-1: What Works

Somewhere in the middle of losing the weight, carrying the groceries in from the car started taking multiple trips, and I was exhausted at the end of it. I used to be adamant about getting every bag in at once.

I knew why. Weight loss pulls from muscle too, along with the fat, and by then I'd been losing weight on a GLP-1 for a while. My goal was to lose the weight, and I was glad it was finally happening. But I didn't want to lose my muscle along with it.

So I went looking for how to do that. Most of what came back in that search was about the drug, and almost none of it told me what to do right then to keep my precious muscle. Here's exactly what I was looking for at the time: what the research shows about muscle on a GLP-1, and what you can do about it, in the order I'd do it.

I couldn't find it in one place back then, so I was left to my own devices to figure it out.

How do you stop muscle loss on a GLP-1?

You probably know by now that weight loss draws on some lean tissue along with fat. When you're losing a lot of weight quickly, getting that loss to zero is very hard, and any plan that promises it is lying to you. But you can absolutely keep more of that lean tissue. Here's how: strength training two or three times a week does the most, protein at every meal comes next, and eating enough, rather than as little as possible, helps too.

The strongest evidence is for training. In six trials of older adults eating less, adding strength training three times a week kept most of the lean mass that dieting alone would have lost (Sardeli et al., 2018). A 2025 joint advisory from four medical and nutrition societies, written specifically about GLP-1 medications, says protein alone is likely not enough without strength training, and suggests strength training at least three times a week alongside regular aerobic activity (Mozaffarian et al., 2025).

Here's the order I'd do it in.

1. Lift something, two or three times a week

This one does the most. Resistance exercise helps preserve muscle during weight loss, and of the approaches researchers have tested, it's the one that also improves strength (Cava et al., 2017). The national guideline for adults is muscle-strengthening work at least two days a week (U.S. Department of Health and Human Services), and the GLP-1 advisory suggests three.

Bands, a pair of dumbbells at home, and bodyweight work all count. Pick a weight where the last couple of reps take real effort, and nudge it up when they stop feeling that way. If two days is what fits your week right now, two days is a good start.

2. Eat protein first

When you're eating less, protein gets harder to hit. Eating it first, before anything else fills you up, is the simplest workaround I know. In a review of 87 diet studies, people who ate more protein while cutting calories kept more lean mass (Krieger et al., 2006). On its own, protein helps keep lean mass but doesn't improve strength (Cava et al., 2017), which is why it sits second, behind training. There's more on getting it in when you're not hungry below.

3. Eat enough, not as little as you can

On a GLP-1, getting through a day on a few bites can feel easy. In a review of diet studies, the steeper the calorie cut, the larger the share of weight lost that came from lean tissue (Chaston et al., 2007). The GLP-1 advisory names the size of the calorie cut and how fast the weight comes off among the things that affect how much lean mass is lost (Mozaffarian et al., 2025). If a few bites is most of what you eat most days, that's worth telling your prescribing provider.

4. Watch your strength, not only the scale

The scale can't separate fat from muscle. Strength can tell you more, and you can check it at home (how is below).

What to know

• The weight loss drives the muscle loss, not something the drug does to muscle. In the SURMOUNT-1 body-scan substudy, about a quarter of the weight lost was lean mass on both tirzepatide and placebo (Look et al., 2025).
• Lean mass isn't all muscle. In diet studies, women who cut calories without an exercise program lost about 1 to 1.5 kg of skeletal muscle for every 10 kg of weight (Heymsfield et al., 2024).
• Strength training is the biggest lever. Protein helps, but a 2025 GLP-1 advisory says protein alone is likely not enough without it (Mozaffarian et al., 2025).
• Strength is the easiest thing to track at home, and in diet research it usually holds even as muscle mass drops (Cava et al., 2017).
• Trials testing strength training and protein on semaglutide and tirzepatide are still running (Alawadhi et al., 2026).

Does a GLP-1 cause muscle loss?

The weight loss does. In a body-scan substudy of a tirzepatide trial, about a quarter of the weight lost was lean mass, and the share was the same in the placebo group. Large weight loss from dieting or bariatric surgery draws on lean mass in a similar way. The medication makes the large weight loss possible.

Those scans covered 160 trial participants, 73% of them women, at the start and at week 72 (Look et al., 2025). The 2025 GLP-1 advisory describes the lean and muscle losses on these medications as tracking the amount of weight lost, and as similar to those seen with bariatric surgery and very low-calorie diets (Mozaffarian et al., 2025).

MRI studies of the muscle itself point the same way. A 2024 review found that the drop in muscle volume on these medications looks about like what you'd expect for the weight lost and the person's age, and that fat inside the muscle tends to go down, which researchers read as better muscle quality (Neeland et al., 2024).

One 2025 study in mice found that semaglutide lowered the force some muscles produced, and its authors say the finding needs to be checked in people (Karasawa et al., 2025). I go into how strength and size can move separately in my piece on why upper arms can look loose or hollow after a big weight loss.

How much muscle do you lose on a GLP-1?

It varies a lot between studies. In some GLP-1 trials, lean mass made up about 15% or less of the weight lost, in others 40% to 60%, and about 25% in the largest tirzepatide body-scan study. Lean mass also counts water, organs and bone, so the share that's muscle is smaller than the lean-mass number.

The range comes from a 2024 review of GLP-1 trials, which points to differences in who was studied, which drug, and other health conditions as likely reasons (Neeland et al., 2024). In the semaglutide STEP 1 trial, people lost 9.7% of their total lean mass over 68 weeks (Wilding et al., 2021).

For muscle itself, the clearest numbers come from diet research. Women with overweight or obesity who cut calories without an exercise program lost about 1 to 1.5 kg of skeletal muscle for every 10 kg of weight (Heymsfield et al., 2024). No GLP-1 was involved, but since the weight loss is what draws on muscle, it's the closest guide there is.

How can you tell if you're losing muscle on a GLP-1?

The scale can't tell you, because it weighs fat and muscle together. Strength is the easiest check at home. Keep track of a few things you lift regularly, like the dumbbell you row with or a case of water, and notice whether they start taking more effort. A body-composition scan, such as DXA, measures lean mass directly.

In people, dieting tends to lower muscle mass without lowering strength, and everyday function often improves as fat comes off (Cava et al., 2017). So if a familiar weight starts feeling heavier, that's specific to you and worth paying attention to. The GLP-1 advisory recommends checking muscle strength, function and body composition when the medication is started (Mozaffarian et al., 2025), which makes it a fair thing to ask your provider about at any point.

I write down the weight on my main lift each week. It's the number that tells me the training and the protein are doing their job.

How do you get enough protein on a GLP-1 when you're not hungry?

Eat it first, while you still have room. Then lean on foods that go down easily when you're not hungry: yogurt, cottage cheese, soups, smoothies or protein drinks. A 2025 advisory from four obesity and nutrition societies suggests these, plus setting a reminder to eat if meals start slipping by without you noticing.

The advisory says these softer foods are often easier to face than heavier ones like red meat, cold cuts or hard cheese (Mozaffarian et al., 2025). On how much, it notes that 1.2 to 1.6 grams per kilogram of body weight a day has been proposed during weight loss, and that researchers haven't settled which body weight to base it on, since using current weight can overshoot.

Protein does its best work alongside training. If you're only going to change one thing this month, make it the lifting, then build the protein around it.

Can you rebuild muscle on a GLP-1?

Direct evidence is still thin. Trials testing strength training and protein in people taking semaglutide or tirzepatide are under way. But I know it's possible, because I did it. When I started, I really struggled to squat the empty bar, and I could do two or three hip thrusts with a 45 lb barbell. A little over six months later, with strength training and a lot of protein, especially first thing in the morning, I was squatting 90 lb. Today, still on a GLP-1, I can squat over 175 lb, and my hip thrust PR is 265 lb. So with hard work and heavy weight, yes. I can attest that it's possible. What is well established: muscle responds to strength training at any age, and training while you lose weight keeps more of the muscle you have. Strength training is how strength comes back.

One of those trials, LEAN-PREP, is assigning 232 adults starting semaglutide or tirzepatide to home strength training three times a week, extra protein, both, or neither, for six months (Alawadhi et al., 2026). Until results like that come in, the evidence comes from people who weren't on these medications. In a review of 49 studies of adults over 50, resistance training added about 1.1 kg of lean mass on average (Peterson et al., 2011).

Outside GLP-1 research, creatine has been studied as an add-on to strength training. In a 2024 review of 12 studies of adults under 50, people who took creatine while strength training gained about 1.1 kg more lean mass (a measure that also counts water) than people who trained without it (Desai et al., 2024). A 2022 review of 35 studies found about the same gain with strength training, almost none (0.03 kg) without exercise, and a split by sex: men gained about 1.5 kg, while women's average gain of about 0.3 kg was small enough that it could have been chance (Delpino et al., 2022). No randomized trial has tested creatine in people losing weight on a GLP-1 yet (Ostojic and Galyean, 2026).

The scale shows the weight coming off, and that part is working. What it can't show is the muscle underneath, the part that carries the duffel through the airport and brings the patio chairs in for your mom before winter. You have more say over that part than the headlines suggest, and most of it comes down to lifting something a few times a week and eating your protein first.

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Written by Morgan Crawley · B.S. in Biology, Drexel University (concentration in Human Physiology) · Background in human physiology and clinical research · Former PCOS Challenge Patient Advisory Board member · Personal GLP-1 user · Founder of GLYM Nutrition

Published October 1, 2026.

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