By Elka Cruz, Accredited Exercise Physiologist
GLP-1 medications have changed the way we approach weight management.
For many people, medications such as semaglutide and tirzepatide can make significant weight loss more achievable. They can be an important part of a person’s overall health plan when prescribed and monitored appropriately.
But there is an important question that doesn’t always get enough attention:
When you’re losing weight, what happens to the muscle and bone you want to keep?
Because successful weight loss isn’t simply about making the number on the scales smaller.
It’s about improving health while maintaining the strength, function and physical capacity you need for the rest of your life.
Do GLP-1 medications cause muscle loss?
This is a little more complicated than a simple yes or no.
When people lose a significant amount of weight whether through medication, dietary changes or other approaches, some of the weight lost can come from lean mass.
Recent research found that lean mass accounted for around 25–39% of total weight lost in people taking incretin-based medications, depending on the medication studied. Importantly, lean mass is not the same thing as skeletal muscle. Lean mass also includes things such as body water and organs, so we shouldn’t automatically assume that all lean-mass loss means clinically significant muscle loss.
Research is also finding that reductions in lean mass don’t necessarily translate into a loss of strength or physical function for everyone.
So the message isn’t:
“GLP-1 medications will make you lose your muscle.”
The better message is:
“If you’re losing a significant amount of weight, protecting muscle and physical function should be part of the plan.”
And one of the best tools we have to do that is resistance training.
Why does muscle matter during weight loss?
Muscle isn’t just about looking strong.
It helps you do almost everything.
Your muscles help you:
- Get out of a chair
- Climb stairs
- Carry the shopping
- Lift and reach
- Get up from the floor
- Maintain balance
- Play sport
- Keep up with your family
- Stay independent as you age
Muscle also plays an important role in metabolic health.
That’s why a weight-loss program shouldn’t only ask:
“How many kilograms have you lost?”
It should also ask:
“How strong are you?”
“How well are you moving?”
“Can you still do the things that matter to you?”
Can strength training help preserve muscle while taking GLP-1 medications?
Yes and this is one of the most important reasons to include resistance exercise during weight loss.
Resistance training gives your muscles a reason to stay strong.
When you challenge a muscle appropriately, you’re providing a stimulus for your body to maintain and adapt that tissue.
A recent 2026 systematic review and meta-analysis found that people undertaking lifestyle interventions combined with resistance training had a lower proportion of their total weight loss coming from lean mass than other approaches studied. The researchers concluded that resistance training, alongside adequate protein and appropriate monitoring, can help preserve lean mass during weight reduction.
This doesn’t mean you need to become a gym person.
Strength training could include:
- Dumbbells
- Resistance bands
- Weight machines
- Bodyweight exercises
- Sit-to-stand exercises
- Step-ups
- Squats
- Lifting and carrying
- Other functional movements
The right exercises depend on your current strength, fitness, health and goals.
Do you need to lift heavy weights?
Not necessarily.
The goal isn’t to walk into a gym on Monday and try to lift the heaviest thing you can find.
In fact, if you haven’t exercised for a while, that’s probably a terrible idea.
Good resistance training is progressive and individualised.
You start at an appropriate level, learn the movements, build confidence and gradually increase the challenge as your body adapts.
Australia’s updated 2026 movement guidelines recommend muscle-strengthening activities on at least two days each week for adults and older adults. They also recommend regular aerobic activity and functional activities that target mobility, balance and coordination.
The important thing isn’t doing the “perfect” workout.
It’s giving your body an appropriate reason to stay strong consistently.
What about bone density during weight loss?
This is another part of the conversation that deserves attention.
Your bones aren’t just a rigid framework holding you up. They’re living tissue that responds to the physical demands placed on them.
Regular physical activity is an important part of supporting bone health, particularly activities that load the skeleton and challenge muscles. This becomes increasingly important as we age and as the risk of osteoporosis and fractures increases.
And while we need more research to fully understand the long-term effects of GLP-1-based weight loss on bone health, recent reviews are highlighting bone health as another important consideration when managing body composition during significant weight loss.
This is another reason we don’t want the weight-loss conversation to become solely about calories and kilograms.
Your bones need to be considered too.
Does losing weight mean you’re at risk of losing bone?
Not necessarily.
Weight loss itself isn’t automatically harmful to your bones, and there are many health benefits associated with achieving a healthier weight.
However, substantial or rapid weight loss can change the mechanical loading placed on the skeleton, while reduced food intake can make it more challenging for some people to consume enough protein and essential nutrients.
For people who already have low bone density or osteoporosis, this deserves particular attention.
The answer isn’t to avoid weight loss.
It’s to make sure the weight-loss strategy also supports muscle, bone and physical function.
What type of exercise is best for bone health?
There isn’t one magic exercise.
For most people, a combination of activities is useful.
This might include:
Resistance training
To challenge muscles and provide loading through the skeleton.
Weight-bearing activity
Such as walking, stair climbing or other appropriate activities where your body works against gravity.
Balance and functional training
To help maintain physical capacity and reduce falls risk as you age.
Aerobic exercise
To support cardiovascular fitness and overall health.
The exact combination should depend on the individual.
Someone with healthy bones who wants to improve their strength will have different exercise needs from someone with osteoporosis, significant frailty, joint pain or a history of falls.
That’s where individual assessment becomes important.
What if I’ve never done strength training before?
That’s okay.
You don’t need to be fit before you start exercising.
In fact, starting from where you are is the whole point.
An Exercise Physiologist can assess your current strength, fitness, mobility, health conditions and goals and then develop a program that matches your ability.
For someone taking a GLP-1 medication, that might mean starting with relatively simple movements and gradually building towards a structured resistance program.
For someone with low bone density, it might mean modifying exercises and progressively introducing appropriate loading.
For someone who is already strong and active, it might mean a completely different approach.
There is no one-size-fits-all GLP-1 exercise program.
How much exercise should you do while taking a GLP-1 medication?
The answer depends on the person.
The Australian 2026 movement guidelines recommend that adults and older adults undertake muscle-strengthening activities on at least two days each week, alongside regular moderate-to-vigorous physical activity and functional activities targeting mobility, balance and coordination.
But guidelines are a starting point not a personalised prescription.
Your exercise needs may be different if you’re:
- New to exercise
- Older
- Experiencing significant weight loss
- Living with chronic health conditions
- Managing osteoporosis or low bone density
- Experiencing joint pain
- Recovering from an injury
- Feeling weak or fatigued
- Already highly active
The right program is the one you can perform safely, consistently and progressively.
Is exercise still important if the medication is working?
Absolutely.
This is perhaps the biggest misconception we want to challenge.
Exercise isn’t something you need to do because your medication “isn’t working”.
Medication and exercise can have different jobs.
GLP-1-based medications can assist with weight management.
Resistance training can help support muscle strength and function.
Weight-bearing and resistance exercise can support bone health.
Aerobic activity can improve cardiovascular fitness.
Balance and functional training can help maintain physical capability.
And nutrition provides the energy, protein and nutrients your body needs to adapt.
These things aren’t competing strategies.
They can work together.
So, what’s the goal?
There is nothing wrong with wanting to lose weight.
For many people, weight loss can be an important step towards better health.
But we think the goal can be bigger than the number on the scales.
Lose the weight you want to lose.
Keep the muscle you need.
Support the bones you rely on.
Build the strength to live the life you want.
Because six months from now, you might be very happy that the scales have moved.
But ten, twenty or thirty years from now, you’ll probably care much more about whether you can still:
Carry your shopping.
Climb the stairs.
Get up from the floor.
Play with your grandchildren.
Travel.
Garden.
Walk.
Work.
And live independently.
Don’t just get smaller. Get stronger.
If you’re taking a GLP-1 medication and aren’t sure how exercise fits into your weight-management plan, an Exercise Physiologist can help you work out where to start and how to progress safely.
At Focus Physio & Co, our Exercise Physiologists can assess your current abilities and develop an exercise program around your health, strength, bone health and goals. Book online here and get ahead of it.
