Is your Mounjaro weight loss making you older?
Peter Paumgardhen | Last update: 23rd May 2025
Weight loss drugs like Mounjaro and Wegovy have transformed how many in the SlimrChat community are taking control of their health, but there’s a new concern making headlines. Could rapid weight loss actually be ageing your body from the inside out? Here’s what the latest research says, what it means for you, and how to stay protected.
Is your Mounjaro weight loss making you older? For many in the SlimrChat community, finally seeing the number drop on the scales feels like a long-overdue win. But research now suggests that rapid Mounjaro weight loss could also speed up ageing.
TL;DR – Quick Take
- Dropping kilos fast on Mounjaro? Great, but you might be losing muscle too.
- One study found up to 39% of the weight lost could be lean muscle, not fat.
- That kind of loss can age your body by 10–20 years, say researchers.
- The fix? Add strength training + more protein.
- We explain why it matters and what to do next
The hidden cost of Mounjaro weight loss
GLP-1 weight loss drugs, like Mounjaro and Wegovy (Ozempic), are helping people achieve dramatic Mounjaro weight loss results in record time.
However, a 2024 study published in The Lancet Diabetes & Endocrinology found that up to 39% of the weight lost through these drugs may be lean muscle, not fat. That’s a lot. And it’s more than what’s typically lost during traditional diet-based weight loss.
Why does it matter? Because muscle isn’t just for lifting weights. It keeps your metabolism running, helps balance and mobility, and protects your body as you age. Research published in the Journal of Cachexia, Sarcopenia and Muscle shows that losing too much muscle, too fast, can mimic 10–20 years of biological ageing.
What’s behind the ‘ageing effect’?
Experts say two things are happening. First, the speed of weight loss triggered by these drugs gives the body little time to adapt, meaning both fat and muscle are lost. Second, the drugs may influence hormones like testosterone and IGF-1, which play a role in preserving muscle mass and youthfulness. This combination can quietly drain your physical strength and energy, even if the scales say you’re doing great.
What to do if your Mounjaro weight loss is costing you muscle
The good news? There are ways to fight back. Experts agree that resistance training and high-protein eating are your best tools.
You don’t need long gym sessions or intense workouts to get started. If you are on a Mounjaro weight loss journey, beginner-friendly resistance training, such as using light weights or resistance bands, can make a big difference. Even short, consistent sessions a few times a week can help protect your muscles while you lose weight.
And when it comes to food, prioritise protein. Think lean meats, dairy, legumes, and protein supplements.
Want to go deeper on Mounjaro weight loss and muscle?
If you are wondering how much protein you actually need, check out our guide here: How much protein do you need for weight loss? It breaks things down in simple terms with no jargon, just helpful advice you can put into action.
On May 31, we are releasing a new article titled ‘Losing weight, losing muscle?’ The risk you need to be aware of explores how GLP-1 treatments can lead to unexpected muscle loss and what you can do to stay strong throughout your journey.
In the meantime, join the conversation in the SlimrChat Forums to share what’s working for you and learn how others manage strength training and protein while on treatment.