Exercise Guide · Updated November 2026
GLP-1 and Exercise: How to Protect Your Muscle While Losing Fat
GLP-1 medications can produce large weight loss, but not all of that weight is fat. In the trial data, roughly a quarter to two-fifths of the weight lost was lean mass, which includes muscle plus organs, bone and water. Here is what the studies show, why it happens, and what major nutrition and obesity groups recommend to limit it.
The Muscle Loss Problem: What the Data Says
Semaglutide (Ozempic/Wegovy)
A 2025 joint advisory from four nutrition and obesity medicine groups, published in the American Journal of Clinical Nutrition, reports that in the STEP 1 trial of semaglutide 2.4 mg, 5.3 kg (38%) of the average 13.6 kg weight reduction was lean body mass and 8.3 kg (62%) was fat. Because muscle is about half of lean mass, the advisory estimates that roughly 20% of the weight lost was muscle.
Tirzepatide (Mounjaro/Zepbound)
A DXA substudy of 160 SURMOUNT-1 participants measured body composition after 72 weeks:
- Body weight decreased 21.3% with tirzepatide (pooled doses) versus 5.3% with placebo
- Fat mass decreased 33.9%
- Lean mass decreased 10.9%
- About 75% of the weight lost was fat and 25% was lean mass, in both the tirzepatide and placebo groups
As simple arithmetic, if 25% of a 40 lb loss were lean mass, that would be 10 lbs. The two trials used different populations and methods, so these numbers shouldn’t be read as a head-to-head comparison.
A 2024 review in Diabetes, Obesity and Metabolism notes that lean mass losses vary a lot between studies, from 40% to 60% of weight lost in some to about 15% or less in others. It also points out that lean mass is not the same as muscle, and that MRI studies suggest muscle changes on these drugs are broadly in line with the amount of weight lost.
Why Does This Happen?
The advisory gives several reasons:
- Rapid weight loss. Losing a lot of weight quickly, by any method, usually removes some muscle along with fat.
- Calorie intake drops sharply. The advisory reports calorie reductions of 16% to 39% in people on GLP-1s.
- Low protein and no strength training. Eating less protein because of low appetite, and not doing strength exercises, can both add to muscle loss.
The good news: muscle loss is not inevitable. Strength training and enough protein are the two levers the advisory highlights. I track my own progress with regular DEXA scans. Our body composition tool can help you understand your numbers and set realistic targets.
The Strategy: Protein + Resistance Training
Protein: How Much and Why
There is no single protein target set for GLP-1 users. The joint advisory says:
- The recommended daily allowance for adults is 0.8 g per kg of body weight per day.
- Higher targets, such as 1.2 to 1.6 g per kg per day, have been proposed during active weight loss.
- It’s unclear whether people with obesity should calculate this from actual weight or an adjusted weight, and using actual weight can overestimate needs.
- Prolonged intake at or above 2 g per kg per day should be avoided.
As an illustration only, 1.2 to 1.6 g per kg for someone weighing 82 kg (about 180 lbs) works out to about 98 to 131 grams a day. Your clinician or a registered dietitian may set a different target. If you have kidney disease, ask before increasing protein.
Practical protein sources: chicken, fish, canned tuna, eggs, Greek yogurt, cottage cheese, tofu, beans and lentils, and protein shakes. Check the nutrition label for the protein per serving, since it varies by brand and portion.
Tip for GLP-1 patients: When your appetite is low, eat the protein part of your meal first. If you can only eat half your plate, make sure the protein was the half you finished. Shakes can help when solid food feels like too much.
Resistance Training: What Works
The advisory’s target: strength training at least 3 times a week, plus at least 150 minutes of moderate aerobic exercise weekly, customized to your fitness level.
You do not need to become a bodybuilder. The goal is to give your muscles a reason to stay while you lose fat.
What to focus on:
-
Compound movements. Squats, deadlifts, presses and rows work several muscle groups at once.
-
Progressive overload. Gradually increase the weight, reps or sets over time.
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Train each muscle group regularly. A 3-day full-body plan is a simple way to meet the advisory’s three sessions a week.
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Do not skip legs. Your lower body contains the largest muscles in your body.
A simple starter program:
| Day | Workout |
|---|---|
| Monday | Squats, bench press, rows (3 sets of 8-12 each) |
| Wednesday | Deadlifts, overhead press, lat pulldowns (3 sets of 8-12 each) |
| Friday | Lunges, incline press, cable rows, core work (3 sets of 10-15 each) |
Adjust the weight so the last 2-3 reps of each set feel challenging but doable with good form. If you’re new to lifting or have joint, heart or other health issues, check with your clinician first, and consider a trainer or physical therapist.
Cardio: Still Important, But Not Enough on Its Own
Cardio improves heart health, and the advisory includes at least 150 minutes a week of moderate aerobic activity. But it says aerobic activity alone has a smaller effect on preserving lean mass during rapid weight loss than programs that include strength work.
The right balance:
- At least 150 minutes a week of moderate cardio (walking, cycling, swimming)
- Strength training on at least three days
- Walking is the easiest option to fit in, even when your energy is low during dose increases
Track Body Composition, Not Just Weight
The scale only tells you one number. It does not tell you whether you are losing fat, muscle or water.
Ways to track body composition:
| Method | What it tells you | Where |
|---|---|---|
| DEXA scan | Fat, lean and bone mass by region | Medical and body composition clinics |
| Bioelectrical impedance (such as InBody) | Estimates of fat and lean mass | Many gyms and clinics |
| Tape measurements | Changes in waist and other sites | At home |
| Progress photos | Visual change | At home |
| Strength log | Whether your lifts are holding up | At home or gym |
The advisory lists bioelectrical impedance as a practical option for monitoring muscle. Prices vary by location, so call ahead.
My approach: I get DEXA scans every 8 to 12 weeks. This shows me exactly how my fat mass and lean mass are changing independently. At my last scan, I was at 181.6 lbs and 21.9% body fat, targeting 165 lbs at 13-15% body fat. The DEXA data tells me whether I am on track or losing too much muscle.
Try our body composition tool to understand what your numbers mean and set targets.
Common Mistakes on GLP-1s
1. Not Eating Enough Protein
GLP-1s cut appetite, and it is easy to eat much less than you need without noticing. Even if you are not hungry, get your protein in. Shakes, Greek yogurt and cottage cheese are easy options when solid food feels hard.
2. Only Doing Cardio
Cardio helps your heart, but by itself it does less to protect muscle. Add strength training.
3. Skipping Exercise Entirely
The medication handles appetite. It does not handle body composition. The advisory recommends prescribing GLP-1s together with a structured exercise program.
4. Eating Too Little
Your appetite is already reduced by the medication. The advisory warns that intakes below about 1,200 calories a day for women and 1,800 for men raise the risk of vitamin and mineral shortfalls. Talk to your clinician or a dietitian if you’re eating very little.
5. Not Tracking
If you only watch the scale, you won’t know whether you’re losing fat or muscle. Regular body composition checks give you data to adjust your approach.
The Exercise Prescription
| Component | What the sources say | Frequency |
|---|---|---|
| Resistance training | Strength exercises, progressive overload | At least 3x/week |
| Moderate cardio | Walking, cycling, swimming | At least 150 min/week |
| Protein intake | 0.8 g/kg RDA, 1.2 to 1.6 g/kg proposed during weight loss, avoid prolonged 2 g/kg or more | Daily |
| Body composition tracking | DEXA or bioelectrical impedance | Every few months |
Track your body composition
Body Comp Tool →The Bottom Line
In the trial data, about 25% (tirzepatide, SURMOUNT-1) to 38% (semaglutide, STEP 1) of weight lost was lean mass. Strength training at least three times a week, at least 150 minutes of moderate cardio, and enough protein are what the 2025 joint advisory recommends to protect muscle.
You do not need a perfect program. You need a consistent one. Track your body composition (not just your weight) so you can adjust. If you are just starting treatment, our GLP-1 side effects guide covers what to expect month by month so you can plan your training around dose changes.
For more on GLP-1 treatment options, compare providers in our directory. If cost is a concern, our cheapest GLP-1 guide breaks down current pricing options.
FAQ
How much muscle do you lose on Ozempic or Mounjaro?
In the STEP 1 trial of semaglutide 2.4 mg, about 38% of weight lost was lean mass. In a SURMOUNT-1 substudy of tirzepatide, about 25% was lean mass. Lean mass includes muscle, organs, bone and water, so muscle loss is lower than these figures. The trials differ, so this isn’t a direct comparison.
Should I exercise on GLP-1 medication?
Yes, if your clinician agrees it’s safe for you. The 2025 joint advisory recommends strength training at least 3 times weekly plus at least 150 minutes of moderate aerobic exercise weekly, adjusted to your fitness level.
How much protein should I eat on Ozempic or Mounjaro?
There is no GLP-1-specific target. The adult RDA is 0.8 g per kg per day, and 1.2 to 1.6 g per kg has been proposed during active weight loss. The advisory says to avoid prolonged intake at or above 2 g per kg. Ask your clinician, especially if you have kidney disease.
Can you build muscle while on GLP-1 medication?
Building new muscle is harder while eating in a calorie deficit, so for most people the realistic goal is keeping the muscle you have. People new to strength training may gain some strength and muscle early on. For details on how tirzepatide and semaglutide compare on muscle preservation, see our head-to-head breakdown.
Does creatine help with muscle preservation on GLP-1s?
We did not find trials testing creatine together with GLP-1 medications, so we can’t say whether it helps here. Supplements are not reviewed by the FDA the way prescription drugs are. Ask your prescriber before starting creatine or any supplement, especially if you have kidney disease.
Related
Guides:
- Cheapest GLP-1 Online · Insurance Coverage · Side Effects
- Mounjaro Dosage Guide · Oral vs Injectable · Exercise and Muscle
- Compounded vs Brand-Name · Without Insurance
- Fat Loss vs Weight Loss · DEXA Scan Results · Mounjaro Plateau · Medicare Coverage · Wegovy Pill vs Injection
Provider Reviews: Ro · Hims · MEDVi · Found · Calibrate
Compare: All Providers · Best GLP-1 Programs · All Guides
What we checked
This AI-assisted public-source desk check reviewed the 2025 joint nutrition advisory on GLP-1 therapy in the American Journal of Clinical Nutrition, the SURMOUNT-1 body composition substudy and a 2024 review on lean mass changes with GLP-1 therapies on November 4, 2026. This is not a clinical review and it is not medical advice. Prices and policies change, so confirm them with the provider or your prescriber before you act.