> ## Content Index > Fetch the complete content index at: https://blog.kevinlieberwirth.com/llms.txt > Use this file to discover other available public pages before exploring further. # How to Keep (and Even Build) Muscle on Ozempic and Mounjaro: A Man's Guide - URL: https://blog.kevinlieberwirth.com/keep-muscle-on-ozempic-mounjaro/ - Published: 2026-07-09T21:03:00.000Z - Updated: 2026-07-10T21:07:31.000Z - Description: Up to 45% of GLP-1 weight loss can be muscle. Here's exactly how much protein to eat, how to train, to keep muscle and lose fat on Ozempic or Mounjaro. - Author: Kevin Lieberwirth - Tags: recomp, glp-1, muscle building **On GLP-1 medications like Ozempic and Mounjaro, a big share of the weight you lose can be muscle, not fat. In the main semaglutide trial, about 45% of the weight lost was lean mass. Two habits protect it: eat 1.2 to 1.6 g of protein per kilo of bodyweight a day, and lift weights two to three times a week. Done right, you can lose fat and keep nearly all your muscle.** *By Kevin Lieberwirth · Last updated: 10 July 2026 · \~7 min read* GLP-1 drugs work. Men who fought their weight for years are finally seeing the scale move. That's a real win, and this article isn't here to talk you out of it. But the scale doesn't tell you *what* you're losing. And the data says a lot of it can be muscle. Here's how to make sure the weight you drop is fat, and how to hold on to the muscle that keeps you strong, capable, and lean. My honest take: for men who are severely overweight, these drugs can be a real breakthrough. Some guys are so heavy they can barely walk, never mind run or lift. For them, losing weight the old way is brutal, and diet alone is often the hardest road of all mentally. A GLP-1 can finally get them over that wall and moving. That's how I see these drugs: a tool to build momentum. Once you can move properly again, use that window to change how you live. The drug gets you going. The lifestyle you build on top of it is what actually lasts. ## Why do GLP-1s cause muscle loss? The drug isn't eating your muscle. The calorie drop is. GLP-1 medications kill your appetite. You eat far less, so you lose weight fast. But when you lose weight in a big hurry and you aren't giving your body a reason to keep muscle, some of that weight comes off your muscle as well as your fat. On top of that, most people on these drugs struggle to [eat enough protein](https://blog.kevinlieberwirth.com/how-much-protein-to-build-muscle/), because they're barely hungry. Low protein plus rapid loss plus no training is the exact recipe for shedding muscle. The good news: every part of that is fixable. ## How much muscle are you actually losing? More than most people expect. Two big trials measured it. In the **STEP-1 trial** of semaglutide (the drug in Ozempic and Wegovy), people lost about **15.3 kg** total. Of that, roughly **6.9 kg was lean mass**, about a **13% drop** in lean tissue. That works out to **45% of the total weight lost coming from lean mass**, not fat. In the **SURMOUNT-1 trial** of tirzepatide (Mounjaro and Zepbound), the picture was a bit better: around **26% of the weight lost was lean mass**. So depending on the drug, somewhere between a quarter and nearly half of your weight loss can be muscle if you do nothing to protect it. That's the number this whole article exists to fix. ## Why losing muscle is a bigger deal than the number on the scale Muscle is not just for looking good with your shirt off, though it does that too. Your muscle drives your metabolism. Lose it, and you burn fewer calories at rest, which makes weight *easier to regain* the moment you stop the drug. Muscle is also your strength, your stability, and a huge part of staying healthy and independent as you age. Drop a lot of it in your 30s or 40s and you feel it later. Here's the trap: someone can hit their goal weight on a GLP-1, look "skinny," and actually be weaker and softer than before. Lower weight, worse body. Protecting muscle is how you avoid that. ## How much protein should you eat on a GLP-1? Aim for **1.2 to 1.6 g of protein per kilo of bodyweight per day.** For a man who weighs 90 kg, that's roughly **110 to 145 g a day.** The hard part is that you won't be hungry, so this takes intention. Two rules make it work: - **Spread it out:** aim for **20 to 30 g of protein per meal**, across three to four meals. Your body uses it better this way, and it's more manageable than one big protein bomb. - **Protein first:** when your appetite is small, eat the protein on your plate before anything else. Meat, fish, eggs, Greek yogurt, a shake. Fill the protein quota, then eat the rest if you have room. If you take one thing from this article, it's this: on a GLP-1, protein isn't optional. It's the single biggest lever you have. ## Do you actually need to lift weights? Yes. This is the other half, and it's not optional either. Protein gives your body the material to keep muscle. Lifting gives it the *reason*. Without the pull of training, your body sees muscle as expensive baggage during a calorie shortage and lets it go. Resistance training tells it to hold on. You don't need much. **Two to three sessions a week**, and about **20 minutes of real, hard work per session** is enough to send the signal. Basic compound lifts, taken close to effort. Cardio is fine for your heart, but it does not protect muscle the way lifting does. The proof is striking. One **2025 study reported** that GLP-1 users who followed a plan with resistance training and proper protein lost about **13% of their bodyweight but only around 3% of their muscle.** Compare that to the 25 to 45% muscle loss in the drug-only trials. Same fat loss, almost none of the muscle cost. If you've just started one, here's what I'd tell you: use the drug to put yourself in a position to make the changes that actually matter. Lose fat, not just weight. And build the habits that keep it off. That's what makes the lasting difference to your health, long after the medication stops. ## Can you actually build muscle on a GLP-1? Sometimes, yes, though let's be honest about it. Building muscle usually needs extra calories, and you're eating in a big deficit. But two groups can genuinely gain muscle while losing fat at the same time (this is called a recomposition): - **Men new to lifting.** If you haven't trained seriously before, your body responds strongly, and you can build muscle even in a deficit. - **Men carrying more body fat.** More fat to pull energy from means more room to build while cutting. If you're already lean and experienced, aim to **keep** your muscle during the drop, then build once your weight settles. Either way, lifting plus protein is the plan. Nothing about being on a GLP-1 changes that. ## What about creatine? Worth taking. **3 to 5 g of creatine monohydrate a day** helps you hold on to strength and muscle while you lose weight, and it's one of the most studied, safest supplements there is. It won't fix low protein or no training, but on top of those two, it helps. ## The simple plan 1. Protein: 1.2 to 1.6 g/kg a day, 20 to 30 g per meal, eaten first. 2. Lift: 2 to 3 times a week, 20 minutes of hard work. 3. Creatine: 3 to 5 g a day. 4. Let your doctor handle the medication. You handle the muscle. Do those four things and the weight you lose will be fat. The strong, capable body underneath stays. ## Frequently Asked Questions ### **How much muscle do you lose on Ozempic?** In the STEP-1 semaglutide trial, about 45% of total weight lost was lean mass (roughly 6.9 kg of a 15.3 kg loss). With tirzepatide (Mounjaro) it was around 26%. Protein and resistance training can cut that loss dramatically, to as little as 3% in one 2025 study. ### **How much protein should I eat on a GLP-1?** Aim for 1.2 to 1.6 g per kilo of bodyweight per day, spread as 20 to 30 g across three to four meals. Eat the protein on your plate first, since appetite is low on these drugs. ### **Can I build muscle while on Ozempic or Mounjaro?** Yes, in some cases. Beginners and people carrying more body fat can build muscle while losing fat (a recomposition). Experienced, leaner lifters should focus on keeping muscle during the loss, then building after. ### **Do I have to lift weights, or is walking enough?** You need resistance training. Walking and cardio are good for health but don't preserve muscle the way lifting does. Two to three short strength sessions a week is enough to send the signal to keep muscle. ### **Should I take creatine on a GLP-1?** It helps. 3 to 5 g of creatine monohydrate a day supports strength and muscle retention during weight loss and is very safe. It works best alongside enough protein and regular lifting, not instead of them. ### **Will I regain the weight if I lose muscle?** It's more likely. Muscle drives your resting metabolism, so losing it means you burn fewer calories and regain weight more easily if you stop the drug. Keeping muscle protects your results long term. --- **Want the training half handled for you?** [Grab a free IRON Method workout program](https://kevinlieberwirth.com/workout?video=iT9hSvwNOEa&ref=blog.kevinlieberwirth.com) — a simple, time-efficient lifting plan that protects your muscle while the weight comes off. (Pair it with the [free calorie & macro calculator](https://iron-method.app/tools/calorie-calculator?video=iT9hSvwNOEa&ref=blog.kevinlieberwirth.com) to lock in your personal protein target.) *Kevin Lieberwirth is a physique coach for men who want to build muscle without living in the gym. At 32 he took a demanding corporate job and lost the two-hour training days his old routine depended on. So he rebuilt his approach: got certified through J3U Physique Coaching, hired a Mr. Olympia competitor as his own coach, and developed the IRON Method around four things that actually build muscle. He now coaches full-time and teaches it on* [*YouTube*](https://www.youtube.com/@kevinlieberwirth?ref=blog.kevinlieberwirth.com)*.* *This article is general education, not medical advice. Talk to your doctor about your medication and before starting a new exercise program.*