Training on Ozempic or Mounjaro: Why Exercise Is Non-Negotiable

Around 2.4 million people in the UK are now on weight loss medication. If you are reading this, there is a decent chance you are one of them, or you are thinking about it. Ozempic, Mounjaro, Wegovy - these drugs genuinely work. The weight comes off, often quickly. But there is a catch that does not get enough attention.

You are not just losing fat. You are losing muscle too. And if you do not do something about that, the number on the scale might look better while your body quietly gets weaker.

The Muscle Problem Nobody Talks About

Here is what the research actually says. When people lose weight on GLP-1 medications like Ozempic or Mounjaro, somewhere between 25% and 40% of the total weight lost can be lean mass - muscle, essentially. That is a huge proportion.

To put it in real terms: if you lose 20kg on Mounjaro, up to 8kg of that could be muscle rather than fat. You weigh less, but you are weaker. Your metabolism slows down. Your risk of injury goes up. And when you eventually come off the medication - as many people do - you are more likely to regain the weight because you have less muscle tissue burning calories at rest.

This is where the term "Ozempic face" comes from. Rapid fat loss without muscle preservation leaves people looking gaunt rather than healthy. The same thing happens throughout the body - people describe feeling "skinny fat," lighter but somehow less fit than before.

The WHO issued updated guidance in December 2025 specifically recommending that GLP-1 medications should be used alongside exercise and dietary changes, not instead of them. That is the World Health Organisation saying: the drug alone is not enough.

What the Experts Recommend

The medical consensus is clear and consistent. If you are taking a GLP-1 medication, you need to be doing resistance training. Not optional. Not "if you feel like it." Non-negotiable.

Here is what the research recommends:

• Resistance training 2-3 times per week minimum. Compound movements that hit multiple muscle groups. Squats, presses, rows, lunges - the fundamentals.
• At least 150 minutes of moderate cardio per week for cardiovascular health and fat burning.
• High protein intake - around 1.6g per kg of bodyweight daily, or roughly 40g per meal.

The UK Active position paper from December 2025 went further, calling on the fitness industry to specifically support people on GLP-1 medications with targeted exercise programmes.

One case series studying patients who combined semaglutide or tirzepatide with structured exercise and adequate protein found that those patients preserved or even increased their lean mass. The drug plus training worked. The drug alone did not.

A Mounjaro user on Reddit put it bluntly: "You gotta train hard and get your protein if you want your body to look and feel good at the end of your journey. If you don't, you risk severe muscle wasting... some of these transformations, while phenomenal, do look worrisome from a longevity perspective."

Why Most Exercise Advice Falls Short

The standard advice for people on weight loss medication is "go for walks and maybe do some weights." And while walking is fine, it does not solve the muscle problem. Walking is low-intensity cardio. It burns calories, it is good for your mental health, and it puts almost zero demand on your muscles.

Running is better for cardiovascular fitness, but it is also purely cardio. Long-distance running can actually accelerate muscle loss if you are already in a calorie deficit from medication.

Weight training alone ticks the resistance box, but for many people, especially those who have been inactive, a gym full of barbells and machines is intimidating. Adherence rates for standalone weight training programmes are notoriously poor.

What you actually need is something that combines resistance work, high-intensity cardio, and full-body muscle engagement - ideally in a format that people genuinely enjoy enough to stick with.

Why Boxing Fits Perfectly

Boxing training is, almost by accident, the ideal exercise for someone on GLP-1 medication. Here is why.

It is resistance training and cardio simultaneously. Every punch is a compound movement. A straight right uses your calves, quads, hips, core, shoulder, and arm in a single kinetic chain. A session on the heavy bag is both resistance work (your muscles are driving force into something heavy) and cardiovascular training (your heart rate stays elevated throughout). You do not need to choose between weights and cardio. Boxing is both.

It works the entire body. Unlike most gym routines where you split muscle groups across different days, a single boxing session hits shoulders, arms, chest, core, back, and legs. The footwork alone - pivoting, stepping, changing angles - provides genuine lower body training. The defensive movements - slipping, ducking, rolling - are essentially core exercises with real-world application.

It builds functional muscle, not bulk. The type of muscle boxing develops is exactly what GLP-1 users need to preserve: lean, functional tissue that supports movement, posture, and metabolic health. Boxing builds the kind of physique that makes you feel strong and move well, not the kind that looks good in photos but cannot climb a flight of stairs.

It burns serious calories. A typical boxing session burns 600-800 calories per hour. That supports the fat loss your medication is already driving, while the resistance component protects your muscle. It is the rare activity that does both well.

People actually stick with it. This matters more than anything else. The best exercise programme is the one you do consistently. Boxing is engaging in a way that treadmills and weight machines are not. There is skill development. There is variety. There is a community of people training alongside you. Nobody has ever described a boxing session as boring.

What a Typical Session Looks Like

If you have never set foot in a boxing gym, a typical session at a community club like ours runs roughly like this:

• Warm-up (10-15 minutes): Skipping rope, shadow boxing, dynamic stretches. Your heart rate comes up gradually and every major muscle group gets activated.
• Technical work (15-20 minutes): Learning and drilling combinations on the pads or bag. This is where the skill element comes in - you are thinking, reacting, and coordinating your whole body.
• Conditioning (10-15 minutes): Circuits mixing bodyweight exercises (press-ups, squats, burpees) with boxing-specific drills. This is the most intense part and where the resistance training component really kicks in.
• Cool-down (5-10 minutes): Stretching and recovery.

That is 45-60 minutes covering cardio, resistance, flexibility, coordination, and balance. The exact combination the experts recommend for people on GLP-1 medications - in a single session.

Practical Considerations

If you are on Ozempic, Mounjaro, or any GLP-1 medication and considering boxing, a few things to keep in mind:

Side effects can affect training. Nausea is common, especially in the early weeks. Many people find that timing their training - avoiding sessions immediately after injection day, eating a light protein-rich meal a couple of hours before - helps significantly. Start with lower intensity and build up.

Protein matters even more. Your appetite is suppressed, but your muscles still need fuel. Prioritise protein at every meal. A shake before or after training can help if you struggle to eat enough. The 1.6g per kg target is a good benchmark.

You do not need to spar. Boxing training for fitness does not require getting hit. Pad work, bag work, and conditioning circuits give you all the physical benefits without stepping into a ring.

Community helps with consistency. One of the biggest challenges people face on weight loss medication is maintaining exercise habits when their appetite and energy levels fluctuate. Training in a group, with coaches who know your name and other members who expect to see you, creates accountability that a solo gym membership cannot match.

The Bottom Line

GLP-1 medications are effective tools for weight loss. The science on that is settled. But the science is equally clear that taking the drug without exercising - particularly without resistance training - leaves you losing muscle alongside fat. That undermines the whole point.

Boxing gives you resistance training, high-intensity cardio, full-body muscle engagement, and an exercise format engaging enough that people actually show up consistently. It is not the only good option, but it is hard to think of a single activity that ticks more of the boxes the experts are recommending.

If you are on Ozempic or Mounjaro and you are not training, start. If you are looking for something more effective and more enjoyable than walking on a treadmill, come and hit something.

Book a free trial session at Honour and Glory Boxing Club.