Do Ozempic, Wegovy and Mounjaro Cause Muscle Loss?
- TTG Staff
- Jun 29
- 6 min read
Updated: Jul 2
Part 1 of Guide to GLP-1 Weight Loss Medications
A client sits down with us and says:
"My doctor has recommended Ozempic."
Or Wegovy.
Or Mounjaro.
Usually, the conversation starts the same way.
Their weight has increased.
Their BMI has moved into a category they don't like.
They've tried diets before.
They've lost weight and regained it.
And now they're considering a medication that appears to be helping thousands of people achieve significant weight loss.
The first thing we tell them is simple:
We're not anti-GLP-1 medication.
These medications have helped many people lose substantial amounts of weight, improve blood glucose control, and reduce health risks associated with obesity.
But there is one question we believe deserves far more attention than it currently receives.
What exactly are you losing?
Because weight loss and body composition are not the same thing.
And understanding the difference could dramatically change how you approach your journey.
What Are GLP-1 Medications?
Ozempic, Wegovy, and Mounjaro belong to a class of medications that influence appetite and food intake.
In simple terms, they help people feel fuller sooner and often reduce overall hunger.
As a result, many people consume fewer calories without feeling like they are constantly fighting cravings.
The outcome can be significant weight loss.
And for many individuals, that can be life-changing.
The challenge is that the scales don't tell us what that weight loss consists of.
The Question Most People Never Ask
When someone loses 15kg, the scales celebrate.
Friends celebrate.
Family celebrates.
Social media celebrates.
Doctors often celebrate.
But the scales only tell us one thing:
The total weight changed.
They don't tell us whether that 15kg consisted of:
Fat
Muscle
Water
Bone mineral
A combination of all four
And that's where things become important.
Because not all weight loss is equal.
In fact, I finished a check-in with a client taking a GLP-1 medication just before writing this article. He was understandably excited because the scales showed he had lost 2.9kg since his previous scan.
If we had stopped there, everyone would have called it a great result.
But when we reviewed his body composition, a different story emerged.
A significant portion of the weight lost had come from active tissue, including skeletal muscle and bone mass, rather than predominantly body fat.
Suddenly, the conversation changed.
We weren't asking,
"How do we lose more weight?"
We were asking,
"How do we preserve more muscle while continuing to improve health?"
That's the question the scales can't answer.
And that's why understanding what you're losing is often more important than understanding how much you've lost.
The Short Answer
Yes.
Research suggests that some muscle loss commonly occurs during weight loss achieved with GLP-1 medications.
However, this requires context.
Because the same thing happens during:
Traditional dieting
Bariatric surgery
Very low-calorie diets
Rapid weight-loss programs
When body weight decreases, some lean mass is typically lost alongside fat mass.
The question isn't whether muscle loss occurs.
The question is:
How much occurs, and can we minimise it?
What Does The Research Show?
One of the reasons GLP-1 medications have become such a hot topic is that the weight-loss outcomes are often impressive.
However, when researchers look beyond the scales, a more nuanced picture emerges.
Studies examining body composition have found that a meaningful proportion of the weight lost during GLP-1 treatment can be attributable to lean mass.
It's important to understand what that means.
Lean mass includes:
Muscle tissue
Water
Organs
Connective tissue
Not all lean mass loss is muscle.
However, muscle loss is a genuine concern during any significant weight-loss intervention.
This isn't unique to Ozempic, Wegovy, or Mounjaro.
It's a challenge associated with losing weight rapidly.
Why Muscle Matters
Many people view muscle as something athletes care about.
In reality, muscle is one of the most important tissues in the body.
Muscle contributes to:
Strength
Balance
Mobility
Physical independence
Exercise capacity
Injury resilience
Healthy ageing
As we get older, maintaining muscle becomes increasingly important.
This is why our goal is rarely:
"Lose as much weight as possible."
Our goal is:
"Improve body composition as much as possible."
Those are not the same thing.
The BMI Problem
This is where many people become frustrated.
BMI only considers:
Height
Weight
That's it.
BMI doesn't know:
How much muscle you have
How much fat you have
Whether you strength train
Your bone density
Your physical capacity
Two people can have identical BMIs and completely different health profiles.
One may have high levels of body fat and low muscle mass.
The other may be strong, active, and healthy.
The BMI calculation cannot tell the difference.
That doesn't make BMI useless.
It simply means it should not be the only metric guiding major decisions.
What We See At The Training Ground
When a member begins a GLP-1 medication, we aren't particularly interested in whether the scales move.
The scales will usually move.
We're interested in what happens underneath the scales.
Questions we ask include:
How much fat is being lost?
Is muscle being maintained?
Is strength improving?
Is physical capacity improving?
Is the person becoming healthier?
Because ultimately, that's the goal.
Not simply becoming lighter.
Becoming healthier.
Why We Use Body Composition Scans
This is one of the reasons we invested in body composition analysis.
Weight alone only tells part of the story.
Body composition monitoring helps us understand changes in:
Fat mass
Muscle mass
Segmental muscle distribution
Bone mass trends
Overall body composition
This allows us to identify trends that a bathroom scale simply cannot detect.
A person may lose 10kg and be thrilled.
But if a significant amount of that weight came from muscle, there may be important conversations worth having.
Likewise, another person may lose less total weight while dramatically improving their body composition.
That's often a fantastic outcome.
Can Muscle Loss Be Reduced?
This is the good news.
While some lean mass loss often accompanies weight loss, there are strategies that may help preserve muscle.
The two most important are:
Resistance Training
Strength training provides your body with a reason to keep muscle.
When the body receives a consistent signal that muscle is needed, it becomes more likely to retain it.
Adequate Protein Intake
Protein provides the building blocks required to maintain and repair muscle tissue.
This becomes particularly important when calorie intake decreases.
Unfortunately, reduced appetite can sometimes make adequate protein intake more difficult for people taking GLP-1 medications.
This is one reason nutrition planning becomes so important.
We See Two Types Of Clients
Over time, we've noticed two common paths.
The First Group
They use the medication as a tool.
The medication helps create momentum.
While weight is coming down, they focus on:
Strength training
Nutrition habits
Protein intake
Sleep
Physical activity
Over time, they develop the lifestyle skills required to maintain their progress.
The Second Group
They remain on the medication long-term.
If that's the path they choose alongside their healthcare team, our role changes.
Now the focus becomes:
Preserving muscle
Maintaining strength
Supporting physical capacity
Monitoring body composition
Both paths can be successful.
The key is ensuring the conversation extends beyond scale weight.
The Better Question To Ask
If you're considering a GLP-1 medication, don't just ask:
"How much weight will I lose?"
Ask:
"How will we monitor what type of weight I'm losing?"
That's a much more useful question.
Because losing fat and losing muscle are not the same thing.
And the scales cannot tell the difference.
The Bottom Line
Ozempic, Wegovy, and Mounjaro can be highly effective tools for weight loss.
For many people, they provide an opportunity to improve their health and quality of life.
However, like any significant weight-loss intervention, some lean mass loss can occur alongside fat loss.
The goal should not simply be to lose weight.
The goal should be to lose weight in a way that preserves:
Muscle
Strength
Physical function
Long-term health
At The Training Ground, we are not anti-medication.
We are not anti-doctor.
We are not anti-weight loss.
We simply believe that weight is only part of the story.
Because the scales tell you how much you've lost. Body composition helps tell you what you've lost.
And that distinction matters.
References
Blundell, J., Finlayson, G., Axelsen, M., Flint, A., Gibbons, C., Kvist, T., Hjerpsted, J. B., & Astrup, A. (2017). Effects of once-weekly semaglutide on appetite, energy intake, control of eating, food preference and body weight in subjects with obesity. Diabetes, Obesity and Metabolism, 19(9), 1242–1251. https://doi.org/10.1111/dom.12932
Davies, M., Færch, L., Jeppesen, O. K., et al. (2021). Semaglutide 2.4 mg once a week in adults with overweight or obesity (STEP 1). The New England Journal of Medicine, 384(11), 989–1002. https://doi.org/10.1056/NEJMoa2032183
Jastreboff, A. M., Aronne, L. J., Ahmad, N. N., et al. (2022). Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). The New England Journal of Medicine, 387(3), 205–216. https://doi.org/10.1056/NEJMoa2206038
Rubino, D., Abrahamsson, N., Davies, M., et al. (2021). Effect of continued weekly subcutaneous semaglutide vs placebo on weight loss maintenance in adults with overweight or obesity (STEP 4). JAMA, 325(14), 1414–1425. https://doi.org/10.1001/jama.2021.3224
Wilding, J. P. H., Batterham, R. L., Calanna, S., et al. (2021). Once-weekly semaglutide in adults with overweight or obesity. The New England Journal of Medicine, 384(11), 989–1002. https://doi.org/10.1056/NEJMoa2032183
Heymsfield, S. B., & Wadden, T. A. (2017). Mechanisms, pathophysiology, and management of obesity. The New England Journal of Medicine, 376(3), 254–266. https://doi.org/10.1056/NEJMra1514009
Murphy, C. H., & Koehler, K. (2021). Energy deficiency and muscle loss during weight loss: Implications for preserving skeletal muscle mass. Nutrients, 13(9), 2893. https://doi.org/10.3390/nu13092893
Morton, R. W., Murphy, K. T., McKellar, S. R., et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine, 52(6), 376–384. https://doi.org/10.1136/bjsports-2017-097608
American College of Sports Medicine. (2022). ACSM's Guidelines for Exercise Testing and Prescription (11th ed.). Wolters Kluwer.
World Health Organization. (2024). Obesity and overweight. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight
Comments