GLP-1 receptor agonists—like semaglutide, liraglutide, and dulaglutide—have exploded in popularity. Originally designed for type 2 diabetes management, they’re now widely used for weight loss, appetite control, and improved metabolic health. As their use grows, so do the questions surrounding how they impact muscle, strength, and long-term fitness.
For nearly 15 years, I’ve been a personal trainer. This is the first year I’ve worked with a large group of clients using GLP-1s. It makes sense—these medications are new, trendy, and extremely effective when used correctly. And I want to start by saying something important:
I am not against GLP-1s. I actually love them when they’re paired with proper nutrition, strength training, and lifestyle changes.
But like any tool, they require the right approach. Over the past year, I’ve trained dozens of clients on GLP-1s. I’ve learned what really helps preserve muscle. I’ve also learned what tends to lead to problems if left unaddressed.
What GLP-1s Do—and Why Muscle Matters
GLP-1s work by mimicking a natural hormone that regulates blood sugar, slows digestion, and increases feelings of fullness. This leads to people eating significantly less, which is why weight loss typically follows.
But with reduced appetite comes one big concern:
Without enough protein and strength training, weight loss can include muscle loss.
Muscle is essential for metabolism, balance, injury prevention, blood sugar control, and overall health. Losing too much of it can slow your progress or even push you backward.
Patterns I’ve Seen Training Clients on GLP-1s
Working with countless clients on GLP-1 medications has provided me with a unique perspective. This experience has shown me what typically happens. It has also highlighted what needs immediate attention.
1. Low Protein Intake Is Extremely Common
Because GLP-1 users feel full very quickly, some struggle to eat enough protein to support muscle. Doctors often give recommended amounts, but sticking to them can be hard with a reduced appetite.
Clients who under-eat protein almost always show declines in lean mass during InBody scans.
On the other hand, I had a client who went to the opposite extreme. She dramatically increased her animal protein intake. As a result, she developed kidney issues. Her doctor switched her to plant-based protein sources, and her symptoms improved quickly.
These experiences taught me that protein needs to be monitored—closely and consistently.
2. Some Clients Go Overboard With Cardio
A surprising number of clients get very motivated by their weight loss. They start doing lots of cardio. This is often far more than their bodies are ready for.
This often leads to:
- Muscle loss
- Fatigue
- Slower metabolism
- Reduced strength
When appetite is suppressed and cardio spikes suddenly, the body tends to burn muscle instead of fat. I see this pattern regularly in clients who lose weight very fast.
3. Monthly InBody Testing Makes a Huge Difference
I use InBody scans every month with all my clients on GLP-1s. It’s one of the most valuable tools we have because it tracks:
- Lean muscle mass
- Body fat mass
- Total body water
- Segmental muscle changes
Instead of guessing, we can see exactly what’s happening. If lean mass drops, we adjust protein and shift training toward more resistance work. If water levels fall, we address hydration. If fat mass is decreasing at the right rate, we know we’re on track.
These scans allow us to personalize the plan before problems get worse.
Why GLP-1 Users Need a Strong Muscle-Preservation Plan
GLP-1s don’t “cause” muscle loss directly. But the combination of:
- Reduced appetite
- Lower food intake
- Over-reliance on cardio
- Inconsistent protein consumption
…creates the perfect environment for it.
Many clinical trials show that people on GLP-1s lose both fat and muscle. But they also show that proper strength training and nutrition dramatically reduce muscle loss.
It’s not the medication—it’s the habits surrounding it.
How I Coach Clients to Keep Muscle While on GLP-1s
When someone on GLP-1s starts training with me, we focus on:
Balanced nutrition
- Adequate daily protein
- Even distribution of protein across meals
- Hydration monitoring
- Plant-based options if necessary
- Avoiding extreme caloric restriction
Smart training
- Strength training 2–3 times a week
- Limiting excessive cardio
- Using progressive overload to stimulate muscle growth
- Building foundational strength before adding volume
Lifestyle and recovery
- Quality sleep (7–9 hours)
- Stress management
- InBody monitoring
- Adjustments based on real data
With the right structure, GLP-1 users not only preserve muscle—they often gain strength, improve mobility, and build better long-term habits.
A Balanced Perspective
GLP-1s offer real benefits:
Better blood sugar control, reduced visceral fat, decreased cardiovascular risk, and improved weight management. For many people, the pros far outweigh the cons.
But without guidance, it’s easy to lose more muscle than you want. That’s why training, nutrition, and monitoring matter so much.
Final Thoughts
GLP-1 medications are powerful tools—not shortcuts. When used responsibly, they can help people transform their health in sustainable ways. This requires pairing them with resistance training, balanced protein intake, and monthly InBody tracking.
My experience training clients on these medications has reinforced one big truth:
You can absolutely lose fat and protect your muscle—but only if you’re intentional about it.
Exercise Science Journey 
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