Is Your GLP-1 Costing You Muscle? What Overland Park Strength Coaches Want You to Know
Is Your GLP-1 Costing You Muscle? What Overland Park Strength Coaches Want You to Know
How GLP-1s work, how much muscle you could lose, and the training and protein habits that help you keep it
Here’s how GLP-1 medications work:
GLP-1 medications like Ozempic, Wegovy, Mounjaro and Zepbound, among others, reduce appetite and slow digestion, so they don't target muscle directly. But a 2026 meta-analysis of 20 clinical trials found that 25% to 39% of the weight people lost on these medications was lean mass, which includes muscle. Strength training and enough protein are the two levers that change that ratio, and both are things you control.
If you live in Overland Park, Leawood or anywhere in Johnson County and are on a GLP-1, you've probably watched the scale move and wondered what's actually leaving your body. Is it fat? Muscle? Perhaps both? Those are the right questions to ask. After all, muscle is what lets you carry groceries, climb stairs, get up off the floor and stay independent as you age.
This guide answers that question with current research, and real-life perspective from our coaches and staff at Alloy Personal Training Overland Park.
A note on our lane:
It’s important to remember that we're strength coaches, not medical providers. We don't weigh in on whether you should take a GLP-1, which one, or at what dose. That's between you and your prescriber. Our job is the part that happens in the gym: helping you keep the muscle you have and build more.
1. What do GLP-1 medications actually do?
GLP-1 (glucagon-like peptide-1) is a hormone your small intestine makes. According to the Cleveland Clinic, GLP-1 medications mimic it by binding to the same receptors and triggering the same effects. They work in three main ways:
1. They tell your brain you're full. GLP-1 acts on the areas of the brain that process hunger and fullness, so you ultimately eat less.
2. They slow digestion. Food leaves your stomach more slowly, allowing you to stay full longer.
3. They help regulate blood sugar. They prompt the pancreas to release insulin and block glucagon, which is a hormone that raises blood sugar.
Semaglutide (sold as Ozempic and Wegovy) targets the GLP-1 receptor. Tirzepatide (Mounjaro and Zepbound) also targets a second gut hormone receptor called GIP.
The practical result is most people eat less, often a lot less. According to a 2025 joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity SocietyPeople on GLP-1s cut their calorie intake by 16% to 39%! That calorie gap drives weight loss, and it's also where the muscle question starts.
2. Do GLP-1s affect muscle growth?
The short answer? Not directly.
A 2026 real-world study of 486 adults on GLP-1s, presented at the European Congress on Obesity, found no sign of clinically relevant muscle wasting. Based on the 2025 joint advisory, the muscle loss people see comes from the conditions the medication creates:
•A large calorie deficit. When your body gets much less energy than it needs, especially when weight comes off fast, it pulls from both fat and lean tissue.
•Low protein intake. A smaller appetite often means less protein, and protein is the raw material muscle needs to repair and rebuild.
•No strength training. Without resistance work, the body has little reason to hold on to muscle.
Fatigue is also a common side effect, which can make it harder to show up for workouts.
Your body keeps muscle when it has a reason to. Resistance training is that reason.
The 2025 joint advisory is direct on this point: more protein alone is likely not enough to preserve muscle without structured strength training.
3. Can you build muscle on a GLP-1?
It's harder in a calorie deficit. For most people, the realistic goal is to preserve muscle while losing fat. Any muscle you build along the way is a bonus.
4. Will I lose muscle mass on a GLP-1?
Perhaps some, and that's true of almost any meaningful weight loss. How much you lose is the part you can influence.
| Approach | Share of weight lost as lean mass | Source |
|---|---|---|
| GLP-1 medications (20 randomized trials) | 25% to 39% | Eisa and Barood, Diabetes, Obesity and Metabolism, 2026 |
| GLP-1 medications (21 trials, 10%+ weight loss) | About 31.5% | Madsen et al., European Congress on Obesity, 2026 |
| Diet and exercise programs | About 14% to 21% | Madsen et al., European Congress on Obesity, 2026 |
| Lifestyle programs that include resistance training | About 18% | Eisa and Barood, Diabetes, Obesity and Metabolism, 2026 |
Here are three things to know before those numbers worry you:
1. Lean mass isn't the same as muscle. It also includes water, bone and organ tissue. Because muscle makes up about half of lean mass, the 2025 joint advisory estimates that roughly. 20% of the weight lost in the STEP 1 semaglutide trial was actually muscle.
2. Fat still goes faster. In the European Congress on Obesity study of 486 adults on GLP-1s, fat mass fell 18% while skeletal muscle fell 5%. Muscle as a share of body weight held steady or improved in more than 70% of patients, a group that also received exercise counseling.
3. Training changes the math. In the 2026 meta-analysis, the lowest lean-mass share belonged to lifestyle programs that included resistance training. That's the gap you can close.
5. Why this matters more after 40.
The 2025 joint advisory notes that muscle and bone loss during weight loss hits harder at older ages and in people who are less active or eat too little protein. Alloy specializes in adults 40 and older, and protecting muscle during weight loss is exactly the kind of work our coaches are built for.
6. How do I keep muscle while taking a GLP-1?
Lift weights, eat enough protein, and recover well. Here's how our coaches approach it with members on a GLP-1:
1. Strength train at least three times a week. That's the target in the 2025 joint advisory, alongside 150 minutes of moderate aerobic activity each week. New to lifting? Start with two full-body sessions and build up. Increase the weight or resistance gradually over months. That progression is the signal that tells your body to hold on to muscle.
2. Start now. Don't wait to "lose a little first." Muscle is easier to keep than to rebuild.
3. Put protein first. When your appetite is small, eat the protein on your plate before anything else. The joint advisory and a 2026 review in the journal Nutrients both point to targets of 1.2 to 1.6 grams per kilogram of body weight per day during weight loss. Your prescriber or a registered dietitian should set your personal number.
4. Don't skip recovery. Sleep and hydration matter more when you're eating less. Both affect how well you train and how well muscle repairs.
5. Keep your prescriber in the loop. Tell them you're strength training. If nausea, dizziness or fatigue is making it hard to eat or train, that's a conversation for them, not us.
Cardio helps, but it isn't enough on its own. Walking and cycling support heart health and energy. But the joint advisory notes that aerobic exercise alone does less to preserve lean mass during rapid weight loss than resistance training does.
At Alloy Overland Park, sessions are coached in small groups or one-on-one, and every workout is scaled to where you are. If a GLP-1 is affecting your energy, your coach adjusts the session to match.
7. How do I know if I'm losing fat or muscle on a GLP-1?
The scale can't tell you. A body composition scan can.
From there, rescans at regular check-ins show the trend:
• Weight down, muscle holding: You're on track. Keep training.
• Weight down, muscle dropping fast: Time to look at training frequency and protein, and a good moment to loop in your prescriber or dietitian.
Every new Alloy Overland Park member starts with a Starting Point session: a conversation about your health history and goals, a physical screening and a sample workout, plus an InBody body composition scan. According to InBody, the scan uses bioelectrical impedance to estimate your fat mass and muscle mass separately, so you see what you're actually losing, not just how much.
That's the same approach medical experts suggest. The 2025 joint advisory calls bioelectrical impedance a practical, low-cost way to track muscle with repeat measurements. It also suggests working with an exercise physiologist or strength trainer to assess strength, build a resistance program and monitor progress.
For the most consistent readings, InBody recommends testing at the same time of day under the same conditions each time, and using your first scan as the baseline.
Ready to find out what you're losing? Book a Starting Point session at Alloy Personal Training Overland Park, 5053 W. 119th St. in Hawthorne Plaza, serving Overland Park, Leawood and greater Johnson County. Bring your questions, and we'll build a plan that works alongside your prescriber's.
GLP-1 and strength training FAQs
Is it safe to lift weights while taking Ozempic, Wegovy or Zepbound?
For most people, yes. A 2025 joint advisory from four U.S. medical and nutrition societies recommends pairing GLP-1 medications with a structured exercise program that includes strength training. Check with your prescriber before starting, especially if you're having side effects.
How often should I strength train on a GLP-1?
At least three times a week, tailored to your fitness level, according to the 2025 joint advisory. Beginners can start with two sessions and build up.
Is walking or cardio enough to keep muscle on a GLP-1?
No. Cardio supports your heart and energy, but the 2025 joint advisory notes that aerobic exercise alone does less to preserve lean mass than resistance training.
Can Alloy coaches tell me how much protein to eat?
We can share general guidance and help you build eating habits that support your training. Your specific protein target should come from your prescriber or a registered dietitian.
I'm over 50. Is it too late to build muscle?
No. Strength training benefits adults at every age, and the 2025 joint advisory notes that protecting muscle during weight loss matters even more at older ages. Alloy's coaching is designed for adults 40 and up.
Do I need to tell my doctor I'm starting a strength program?
Yes. Your prescriber should know about any major change in activity while you're on a GLP-1.
This article is for general education and isn't medical advice. Alloy coaches don't advise on medications or dosing. Talk with your prescriber about any questions related to your GLP-1 treatment.
Sources:
• Cleveland Clinic. GLP-1 Agonists. Medically reviewed health library article.
• Mozaffarian D, et al. Nutritional Priorities to Support GLP-1 Therapy for Obesity: A Joint Advisory From the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society. American Journal of Lifestyle Medicine, 2025.
• 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.
• Madsen LB, et al. Effects of Incretin-Based Therapies, Diet and Exercise Interventions, and Bariatric Surgery on Fat-Free Mass in Adults with Overweight or Obesity. European Congress on Obesity, 2026. Summarized by epocrates.
• Frohner EI, et al. Preservation of Skeletal Muscle Mass During GLP-1 Receptor Agonist and GIP/GLP-1 Receptor Agonist Therapy in Adults with Obesity. European Congress on Obesity, 2026. Summarized by epocrates.
• Reytor-González C, et al. Higher-Protein Nutrition and Concurrent Exercise in Obesity. Nutrients, 2026.
• InBody USA. InBody Test.
