Guide
Ozempic, Wegovy or Mounjaro: what the lean mass data shows
Which medication you take is your prescriber's call. What 20 pooled trials found about lean mass, why the table is not a league table, and how each one changes the shape of your week.
The short answer
Which medication you take is your prescriber's decision, and this page will not try to influence it. Pooled across 20 randomised trials, the lean share of weight lost was 35.2% on semaglutide, 25.4% on tirzepatide and 26.8% on liraglutide. Diet alone cost 26.2% and resistance training took it to 17.5%. The last two numbers are the ones you control, and they move the result further than the choice of molecule does.
Start with your protein numberThe five medications, side by side
| Medication | Molecule | Schedule | Lean share of weight lost pooled, 20 trials | Confidence interval |
|---|---|---|---|---|
| Ozempic | semaglutide | once a week | 35.2% | 31.5 to 38.9% |
| Wegovy | semaglutide | once a week | 35.2% | 31.5 to 38.9% |
| Mounjaro | tirzepatide | once a week | 25.4% | 22.8 to 28.0% |
| Zepbound | tirzepatide | once a week | 25.4% | 22.8 to 28.0% |
| Saxenda | liraglutide | once a day | 26.8% | 23.1 to 30.5% |
| No medication | diet alone | every day | 26.2% | 24.1 to 28.3% |
| Any of them, plus lifting | resistance training | twice a week | 17.5% | 14.2 to 20.8% |
Every figure in that table comes from the same 2026 meta-analysis of 20 randomised trials and 15,782 participants, which is why they can be read against each other. Eisa N et al, Diabetes, Obesity and Metabolism 2026
Ozempic and Wegovy are the same molecule at different approved dose ranges. Mounjaro and Zepbound are likewise the same molecule under two brand names. So the real comparison is between three molecules, not five products: semaglutide, tirzepatide and liraglutide.
The two rows at the bottom are the ones worth staring at. Losing the same weight through diet alone cost 26.2% as lean mass, which was not significantly different from the medications (p = 0.42). The muscle comes off because the weight comes off, not because of the injection. Eisa N et al, Diabetes, Obesity and Metabolism 2026
Why that table is not a league table
A percentage of a larger loss can be more absolute kilograms of lean tissue than a larger percentage of a smaller loss, which is the trap when people quote these numbers at each other online. The pooled figures also carry wide confidence intervals and the studies behind them disagree with each other more than most health articles admit, so read them as the shape of the problem rather than as your personal forecast.
There is a further catch in the potency. The medications that take off the most weight and the most fat were among the least effective at holding on to lean mass, so a bigger number on the scale is not the same as a better result. That is a network meta-analysis finding rather than a coaching opinion. Karakasis P et al, Metabolism 2025
Most importantly, almost nobody in those trials was given a protein target or a training programme. What the table measures is what happens to lean mass when a large deficit arrives and nothing else changes. That is the default outcome, not a ceiling. In the people we coach, the difference between eating 60 g of protein a day and 110 g with two sessions a week is larger than the difference between the two molecules.
What semaglutide does to your week
Semaglutide has a half-life of about a week and blood levels peak one to three days after the injection. In practice that gives most people a rhythm: two harder days where volume is difficult and nausea is most likely, then three or four days where eating is more normal. The appetite effect on semaglutide behaves like a dimmer switch that is turned down further at each dose step.
The plan that follows is opportunistic. Put your largest protein meals and your strength sessions in the second half of the week, keep the first two days lean, small and liquid if you need to, and protect the evening before the next dose as a cooking and eating window. See the night before your injection and injection day, what to eat.
Wegovy runs the same molecule at higher strengths, which is where the lowest intakes we see occur. At the top of that range a shake stops being a convenience and becomes the backbone of the day. The guide on hitting protein on 800 calories is written for exactly that situation.
What tirzepatide does to your week
Tirzepatide acts on two gut hormone pathways, GLP-1 and GIP, and has a half-life of about five days. The effect is flatter across the week than semaglutide's, and the people we coach describe it less as nausea and more as food simply becoming irrelevant. Nothing is unpleasant; nothing is interesting either.
That changes the failure mode. On semaglutide people miss protein because they feel sick. On tirzepatide they miss it because nothing reminds them to eat. The answer is a clock rather than a plan: a fixed protein breakfast, a fixed shake, a fixed dinner, whether or not you feel like any of them. Weight also tends to come off faster on tirzepatide, and faster loss is where a quarter of the total still adds up to a lot of muscle.
Liraglutide and compounded products
Saxenda is liraglutide, injected daily, with a half-life of about 13 hours. Its appetite effect is milder and steadier than the weekly medications, which usually means slower loss and a smaller deficit, and in practice a gentler ride for lean mass. There is no weekly window to exploit, so consistency does the work: three protein servings a day at the same times.
Compounded semaglutide and tirzepatide behave like the branded versions on appetite, but the strength and the way they are stepped up vary between pharmacies. If you are on one, make sure your prescriber knows exactly what you are taking, and follow the same food and training plan as you would on the branded product. Our compounded GLP-1 guides cover the same situations.
Side effects decide what you can eat
The medication that protects your muscle best is, in practice, the one whose side effects still let you eat protein. Nausea is the side effect reported most often across this whole class, and constipation, reflux and loose stools show up with all of them, most heavily in the weeks after a step up. Which of them you get, and how hard, is the thing that actually decides your protein average.
Each of those pushes people towards low-protein food: dry toast, crackers, soup, tea. Two weeks of that is the commonest route to a falling strength test that we see, and it has nothing to do with which molecule you were prescribed. The food answers for each symptom are collected in GLP-1 side effects: what to eat.
Dose steps are the weeks protein disappears
Every one of these medications is stepped up over time, and the pattern differs. Wegovy usually steps through several strengths. Mounjaro and Zepbound start low and hold for a few weeks before each step. Saxenda steps more often at the start. Each step tends to bring a few days where you eat noticeably less, then a settling.
Plan for it rather than being surprised by it. In a step week, drop your ambitions for whole-food meals, keep a shake and a yoghurt as the floor, and keep both strength sessions even if you shorten them. See dose increase week for the two-day plan we use.
What none of these trials measured
One more thing belongs on a page that compares medications, because no manufacturer's material will tell you. In a 2026 review of 35 studies in the Annals of Internal Medicine, not one reported whether people could actually do more or less afterwards. Scans were measured. Getting out of a chair was not. Batsis JA et al, Annals of Internal Medicine 2026
Every figure in the table above came off a scan. Not one of those studies checked whether the people in them could stand up more easily, carry more, or climb stairs without stopping. So compare the molecules if you like, and then measure the thing the trials did not: your own strength test, same movement, same way, every week. We are comparing you with you, and we do not diagnose anything from it.
What actually decides your lean mass
Your protein average across the week
1.2 to 1.6 g per kg of goal weight, spread at 0.3 to 0.4 g per kg a meal. This is the single biggest lever and it is entirely yours, on any medication.
Whether you train twice a week
Six movements, 30 minutes, load heavy enough that the last two repetitions are hard. Walking does not count for this purpose.
How fast you are losing
Rate is a prescriber conversation. Faster loss takes more from everywhere, including bone and muscle.
How long you stay on it, and what happens after
Regain after stopping arrives mostly as fat. Muscle only returns if you make it. See coming off a GLP-1.
If you switch medications
Switching is common and it is entirely your prescriber's decision, including where you restart afterwards. From the coaching side, expect the rhythm of your week to change rather than the targets. Moving from semaglutide to tirzepatide usually flattens the weekly cycle, so shift from opportunistic eating to fixed times. Moving the other way usually sharpens it, so plan around the two days after the injection again.
Keep the same protein number through any switch, keep the two sessions, and keep the weekly strength test running so you can see what the change did. Four weeks of the same three numbers across a switch is far more useful than any comparison you will read online.
Questions people ask
Which GLP-1 is best for keeping muscle?
Pooled across 20 trials the lean share of weight lost was 35.2% on semaglutide, 25.4% on tirzepatide and 26.8% on liraglutide, with wide and overlapping confidence intervals. Almost nobody in those trials was given protein or training. Your prescriber chooses the medication; you choose the two things that move the number most.
Are Ozempic and Wegovy different for muscle?
They are the same molecule at different approved dose ranges, so the pooled lean-mass figure is the same for both. The higher range produces lower intakes, which makes hitting your protein target harder. The target itself does not change.
Is Mounjaro better than Ozempic for body composition?
The pooled figure is lower for tirzepatide, 25.4% against 35.2%, and tirzepatide also produces larger total losses, so the absolute kilograms are closer than the percentages suggest. Treat it as the shape of the problem rather than a ranking.
Does switching medication reset muscle loss?
No. What changes is the rhythm of your week and often the rate of loss. Keep the same protein target and the same two sessions through a switch, and let the weekly strength test tell you what happened.
Do compounded versions behave differently?
On appetite they behave like the branded molecules. Strength and the way they are stepped up vary between pharmacies, so tell your prescriber exactly what you are taking and follow the same food and training plan.
The figures in the table, and where they come from
One meta-analysis supplies every number in the comparison, which is what makes them comparable. The last line is what none of the trials looked at.
Across 20 randomised trials, an average of 35.2% of the weight lost on semaglutide (Ozempic, Wegovy) was lean mass. Eisa N et al, Diabetes, Obesity and Metabolism 2026
Pooled across 20 randomised trials, 25.4% of the weight lost on tirzepatide (Mounjaro, Zepbound) was lean mass. Eisa N et al, Diabetes, Obesity and Metabolism 2026
Losing the same weight through diet alone cost 26.2% as lean mass, which was not significantly different from the medications (p = 0.42). The muscle comes off because the weight comes off, not because of the injection. Eisa N et al, Diabetes, Obesity and Metabolism 2026
Adding resistance training brought the lean share of weight lost down to 17.5%, the most favourable result of any approach studied. Eisa N et al, Diabetes, Obesity and Metabolism 2026
In a 2026 review of 35 studies in the Annals of Internal Medicine, not one reported whether people could actually do more or less afterwards. Scans were measured. Getting out of a chair was not. Batsis JA et al, Annals of Internal Medicine 2026
The papers these numbers come from
- Eisa N, Barood O. Lean Mass Changes With Incretin Therapy Versus Lifestyle Intervention: A Systematic Review and Meta-Analysis of Randomised Controlled Trials. Diabetes, Obesity and Metabolism, 2026. 20 randomised controlled trials, 15,782 participants. doi:10.1111/dom.70666
- Batsis JA, Gavras A, Gross DC, et al. Effect of Incretin-Based and Nonpharmacologic Weight Loss on Body Composition: A Systematic Review. Annals of Internal Medicine, 2026. 35 studies, median duration 26 weeks. doi:10.7326/ANNALS-25-00478
- Karakasis P, Patoulias D, Fragakis N, Mantzoros CS. Effect of glucagon-like peptide-1 receptor agonists and co-agonists on body composition: Systematic review and network meta-analysis. Metabolism, 2025. 22 randomised controlled trials, 2,258 participants. doi:10.1016/j.metabol.2024.156113
Last reviewed 18 September 2026. We update these figures when a larger or better study replaces them, and we say what changed. How we handle evidence.
The free tools that go with this
- The protein calculator Your daily target in grams from your goal weight, with a sample day at that number.
- The protein cheat sheet One page, forty foods, grams of protein per serve in metric and imperial.
- The muscle or fat quiz Six questions that tell you whether what you are losing is the tissue you wanted to lose.
- The Personal 7-Day Plan Your week of meals built to your target and your appetite, A$19 / US$12 / £9.
The Keep Muscle Kit
One system, whichever medication you are on
The workbook, Sunday numbers tracker, 2-day strength plan, injection-day card, and meal plans at 100, 120 and 140 g protein. Instant download.
A$47 / US$29 / £23, one payment.
Read next
- Guide
Protein on a GLP-1
The target in grams, the per-meal number, and how to hit it on a few bites a day.
- Guide
Strength training on a GLP-1
Two 30-minute sessions a week, six movements, and how to start from nothing.
- Guide
Muscle loss on a GLP-1
What the trials found, how to tell whether it is happening to you, and the two fixes.
- Guide
High-protein foods for a small appetite
Ranked by protein per 100 g, with the serve size that gets you to 30 g.
- Guide
A 1,200 calorie GLP-1 meal plan
Seven days at 1,200 calories and 110 g of protein, in grams and ounces.
- Guide
GLP-1 side effects: what to eat
Nausea, constipation, reflux, fatigue and cramps, with the food answer for each.
- Guide
Over 50 on a GLP-1
Why the muscle maths changes after 50, and the weekly plan that protects you.
- Guide
Coming off a GLP-1
What the trial extensions show about regain, and the step-down plan we use.
- Guide
GLP-1 and menopause
Muscle, bone and protein when oestrogen and a calorie deficit pull the same way.
- Guide
Food noise and cravings on a GLP-1
Why the quiet fades late in the dose week, what a craving usually means, and how to eat through it without losing muscle.
- Guide
Fatigue and energy on a GLP-1
The four causes of feeling flat, the three-day test that finds yours, and the day of eating that lifts it.
- Guide
GLP-1 for men over 50
Why muscle goes faster after 50, the protein and training that hold it, and the numbers that matter more than the scale.
- Guide
A GLP-1 on a budget
Protein per dollar, training at home with no equipment, and why you do not need a single supplement.
- Guide
Your first 90 days on a GLP-1
The month-by-month plan: what to set up in week one, what each dose step brings, and what to measure every Sunday.
EverStrong provides nutrition and strength coaching and education. It is not medical advice and does not replace your prescribing doctor. Consult your doctor before starting a new exercise or nutrition plan, especially with a heart, kidney, liver or metabolic condition, if pregnant, or with a history of disordered eating.