Why I'm Writing This Post
I'm Matthew, the owner of Muscles Matter, and I've been getting a LOT of questions lately about Mounjaro. Specifically, people want to know how to keep their hard-earned muscle while the weight drops off.
And just so you know where I'm coming from, I'm on Mounjaro myself and I've currently lost 6 stone on it.
And I get it. I really do.
As an ex-rugby player who had to completely rebuild my body after a serious injury, I understand what it feels like to watch your strength slip away. It's frustrating. It's demoralising. And honestly, it can make you want to give up entirely.
But here's the thing, whether you're recovering from injury like I did, or you're on a Mounjaro diet and worried about losing muscle alongside the fat, the solution is pretty much the same. You need a smart approach to strength training and nutrition.
So let me walk you through exactly what I tell my online coaching clients when they come to me with this exact problem.
The Hidden Problem With Weight Loss Medications
Let's be honest about something first. Mounjaro works. It really does help people lose weight, and for many folks, it's been life-changing.
But there's a catch that not enough people are talking about.
Research shows that as much as 34-39% of the weight you lose on Mounjaro could be lean muscle mass. That's a massive chunk of the good stuff disappearing along with the fat.
Why does this matter? Well, muscle isn't just about looking toned or being able to lift heavy things. Your muscle mass directly affects:
- Your metabolism – Less muscle means you burn fewer calories at rest
- Your long-term weight maintenance – It's harder to keep weight off without adequate muscle
- Your daily function – Everything from climbing stairs to carrying shopping bags gets harder
- Your bone health – Muscle supports your skeleton and reduces injury risk
I've seen it happen. People lose three stone on the scales, feel great initially, then wonder why they still feel weak and tired. The answer? They've lost too much muscle along the way.
The good news is that muscle loss prevention is absolutely possible. You just need the right strategy.
Why Strength Training Is Your Best Friend
Here's where I get excited. Because this is what I do as a personal trainer, and I LOVE helping people discover how powerful resistance training can be.
When you're on Mounjaro, your body is in a calorie deficit. That's how the weight comes off. But your body doesn't automatically know the difference between fat and muscle when it's looking for energy. It'll happily burn both.
Strength training sends a clear signal to your body: "Hey, we need this muscle. Don't touch it."
It's like putting a "Do Not Disturb" sign on your lean tissue. Your body then prioritises fat burning instead.
And before you panic, no, you don't need to become a gym rat. You don't even need a gym membership.
Your Practical Training Plan
Right, let's get into the specifics. This is the framework I use with my online coaching clients who are managing their Mounjaro diet alongside their training.
How Often Should You Train?
Aim for 2-3 resistance training sessions per week. That's it. No need to live at the gym.
Each session should target all major muscle groups:
- Legs and hips
- Chest and back
- Arms and shoulders
- Core
You want to hit each muscle group at least twice a week for optimal muscle retention.
What Exercises Should You Do?
Focus on compound movements, exercises that work multiple muscle groups at once. These give you the biggest bang for your buck:
- Squats (bodyweight or weighted)
- Lunges (forward, reverse, or walking)
- Press-ups (modify on your knees if needed)
- Rows (with resistance bands or dumbbells)
- Deadlifts (even with light weights, the movement pattern matters)
- Overhead presses
For each exercise, aim for 8-12 repetitions across 2-3 sets. The last few reps should feel challenging but doable with good form.
The Secret Sauce: Progressive Overload
This is the bit most people miss.
Your body adapts quickly. If you're doing the same exercises with the same weights week after week, your muscles have no reason to stick around.
Progressive overload means gradually making things harder over time. You can do this by:
- Adding a small amount of weight
- Doing an extra rep or two
- Adding another set
- Slowing down the movement
Even tiny improvements count. Trust me on this.
Rest and Recovery
Here's something else I learned the hard way during my rugby injury recovery, rest is when the magic happens.
Your muscles don't grow during your workout. They grow during recovery. So give yourself 48 hours between sessions targeting the same muscle groups.
And please, prioritise 7-9 hours of sleep each night. I know it sounds basic, but muscle repair and hormonal balance happen primarily during deep sleep. Skimp on sleep, and you're undermining all your hard work in the gym.
Nutrition: Protein Is Non-Negotiable
You can train perfectly, but if your nutrition isn't supporting your goals, you'll struggle.
When you're on Mounjaro and trying to prevent muscle loss, protein becomes your absolute priority.
How Much Protein Do You Need?
Aim for 1.2-1.6 grams of protein per kilogram of your body weight each day.
So if you weigh around 75kg, you're looking at roughly 90-120 grams of protein daily.
That might sound like a lot, but when you spread it across your meals, it's very achievable.
Where Should You Get Your Protein?
Focus on high-quality sources at every meal:
- Chicken and turkey
- Fish (salmon, cod, tuna)
- Eggs
- Greek yoghurt
- Lean beef
- Legumes and beans
- Tofu and tempeh
Pro tip: After your training sessions, try to get 20-30 grams of protein within 30 minutes. This is when your muscles are crying out for amino acids to start the repair process.
Other Things That Actually Help
Beyond training and protein, here are a few more strategies I recommend:
Stay Hydrated
Mounjaro can affect your digestive system, so proper hydration is even more important. Aim for 2-2.5 litres of water daily. Your muscles need it to function properly, and it supports your recovery between sessions.
Monitor Your Progress
Don't just rely on the scales. The number might go down, but that doesn't tell you whether you're losing fat or muscle.
Consider:
- Taking body measurements every few weeks
- Progress photos (they don't lie)
- Tracking your strength in the gym (are your lifts improving?)
- Bioelectrical impedance scales that estimate body composition
If you notice your strength dropping significantly or measurements changing in ways you don't like, it might be time to adjust your approach.
Work With a Professional
Look, I'm obviously biased here. But working with a personal trainer who understands the nuances of training while on weight loss medication can make a huge difference.
This is exactly what I do with my online coaching clients. We create personalised plans that account for your specific situation, your energy levels, and your goals.
You've Got This
Here's what I want you to take away from this post.
Mounjaro can be an incredible tool for weight loss. But without the right support: specifically, consistent strength training and adequate protein: you risk losing the muscle that keeps you strong, healthy, and metabolically active.
The good news? Muscle loss prevention isn't complicated. It just requires consistency and a smart approach.
Train 2-3 times per week. Focus on compound movements. Eat enough protein. Rest properly. And consider getting support from someone who's been through their own physical challenges and come out the other side.
That's exactly what I did after my rugby injury. And now, helping others do the same is what gets me out of bed every morning.
If you're on Mounjaro and want a training plan that actually works for your situation, get in touch. I'd love to help you keep your muscle while the fat disappears.
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