In brief
- GLP-1 medications like Mounjaro and Wegovy are highly effective – but with rapid weight loss, some muscle can be lost alongside fat
- For women in perimenopause and menopause, protecting muscle is especially important because oestrogen decline already makes this harder
- The good news: eating enough protein and doing regular strength-based movement are proven to protect your muscle during treatment
- CheqUp’s Health Coaches and WW app integration are specifically designed to help you do both, without making it complicated
What is muscle loss on GLP-1 medication?
GLP-1 medications – including Mounjaro (tirzepatide) and Wegovy (semaglutide) – represent a genuine step change in how we treat weight. Clinical trials show average weight loss of 15–21% of body weight over 72 weeks, with many people losing considerably more.¹ These are results that, until very recently, were only achievable through surgery. It’s an exciting time.
But there’s a nuance worth understanding, and at CheqUp we think you deserve the full picture: when you lose weight – whether through medication, diet, or surgery – not all of it comes from body fat. A proportion comes from lean tissue, including muscle. Research suggests this proportion can be anywhere from a quarter to a third of total weight lost.²·³ That’s not a reason to stop treatment, and it doesn’t happen to everyone in the same way. But it is worth paying attention to – especially if you know how to act on it.
Why does rapid weight loss cause a loss of muscle?
The mechanism is straightforward. GLP-1 medications work by reducing appetite and slowing how quickly food leaves the stomach. You eat less. Your body draws on stored energy to make up the difference. In a calorie deficit – which is the intended effect – your body doesn’t perfectly distinguish between burning fat and breaking down muscle protein. It does some of both.
The faster the weight loss, and the lower your protein intake, the more likely your body is to dip into muscle reserves. This is not unique to GLP-1 medications – it’s a well-established feature of any significant calorie reduction. The good news is that it’s genuinely manageable with the right support in place.
Why does muscle mass matter more if you’re in perimenopause or menopause?
This is where the conversation becomes particularly important for a lot of the women we see at CheqUp. Muscle mass is not a vanity consideration – it is a core pillar of long-term health. And for women going through the hormonal changes of perimenopause and menopause, it deserves serious attention.
Oestrogen plays an important but often overlooked role in maintaining muscle. It supports muscle protein synthesis – the process by which your body builds and repairs muscle tissue. As oestrogen levels decline during perimenopause, this process becomes less efficient. The NHS lists muscle aches and joint pain among the common physical symptoms of menopause,⁴ and research confirms that women in this life stage lose muscle mass at an accelerated rate compared to men of the same age – a process that can begin as early as the mid-forties.⁵
When you then add the muscle-reducing effect of a significant calorie deficit on top of this hormonal context, the stakes are higher. Here’s why it matters beyond how your body looks:
Metabolism
Muscle is metabolically active tissue – it burns energy even at rest. Less muscle means a slower metabolic rate, which can make it harder to maintain weight loss once treatment ends or doses are reduced.
Joint health
Muscle supports and stabilises your joints. Losing muscle while losing weight can increase strain on knees, hips, and the lower back – areas that the NHS notes are already commonly affected by menopausal symptoms.
Bone density
Strength-based movement is one of the best-evidenced ways to protect bone density during and after the menopause – the same activity that protects muscle protects your skeleton.⁶
Energy and confidence
Many of our members describe a loss of energy and physical confidence during perimenopause. Maintaining muscle directly supports how strong and capable your body feels day to day.
Preserving muscle isn’t a complication of your weight loss journey – it’s what makes the weight loss meaningful and lasting.
How do I protect muscle on a GLP-1?
The research is increasingly clear on this. Two things, used together, are the most effective tools for protecting lean mass during weight loss: adequate dietary protein and regular resistance-based exercise.
A 2026 clinical trial protocol published in BMJ Open – the LEAN-PREP study, specifically designed to study muscle preservation in people on semaglutide and tirzepatide – is investigating protein targets of 1.6g per kilogram of body weight per day, alongside home-based resistance exercise three times per week.3 The authors note that GLP-1 weight loss “results in dramatic reductions in lean mass” and that “solutions to mitigate this loss of muscle mass and strength are needed.” This trial is designed precisely because the research community agrees that medication alone is not the complete answer.
What does this look like in practice? For a woman weighing 80kg, a protein target of around 1.6g/kg means roughly 128g of protein per day. For context, a chicken breast contains around 30g, a Greek yoghurt around 10–15g, and a serving of lentils around 18g. It’s achievable – but it does require some planning, particularly when appetite suppression from the medication means you’re eating less overall. This is one of the most common challenges our members face, and one of the things that the CheqUp Health Coach team is specifically built to help with.
Please note: patients with certain conditions such as chronic kidney disease (CKD) or certain liver diseases must limit protein intake and should discuss with their prescriber on recommended limits of protein intake/day.
On movement: resistance exercise doesn’t have to mean a gym membership or heavy lifting. Walking with purpose, bodyweight exercises at home, resistance bands, and yoga with strength elements all count. Three sessions a week targeting the major muscle groups is often a helpful, evidence-informed goal, but this can be adapted depending on your current fitness, mobility, energy levels, and lifestyle. At CheqUp, you can book PT sessions with our brilliant Health Coaches, who tailor support to you and help you build a realistic strength routine that works with your body, not against it. There’s no one-size-fits-all approach here.
How CheqUp helps you protect your muscle
This is precisely where a programme built around you – rather than just a prescription – makes a real difference.
Your CheqUp Health Coach understands how GLP-1 medication, appetite, muscle, lifestyle and health factors interact to influence your progress.
From your first session, they’ll work with you to set a realistic protein target and identify foods you actually enjoy that will help you hit it. They’ll also guide you on movement – not with a one-size-fits-all workout plan, but with something designed for your current fitness level, schedule, and any joint or energy challenges you’re navigating alongside your treatment.
Our integration with the WW app gives you a practical, everyday tool to track your protein intake and build the habits that protect your lean mass over time. You can log meals, track your nutrition, and see clearly whether you’re hitting the targets that matter – not just your total calories. The scales tell you one number. The WW app helps you understand what’s behind it.
Medication, coaching, and nutrition tracking help shift the focus beyond just the number on the scales, helping you transform body composition and improve health markers like waist-to-hip ratio. All measures of progress count, but long-term lifestyle changes are what truly last.
Frequently asked questions
Will I definitely lose muscle on GLP-1 medication?
Not necessarily – and it varies considerably between individuals. People who maintain higher protein intake and do regular resistance exercise during treatment can significantly reduce lean mass loss, and some maintain it almost entirely. The risk is highest in people who lose weight very quickly, eat low amounts of protein, and are largely sedentary. Your CheqUp Health Coach will help you identify and reduce these risks from the outset.
How do I know if I’m losing muscle rather than fat?
Weight on the scales alone won’t tell you. Signs that your muscle mass may need a little more support can include feeling more tired with everyday tasks, noticing reduced strength, or feeling like your progress has slowed. If any of these sound familiar, your Health Coach can help you review factors like protein intake, nutrition, and strength-based movement in a way that works best for you.
Does this mean I should avoid GLP-1 medication?
Absolutely not. The overall benefits of these medications – for weight, metabolic health, cardiovascular risk, and inflammatory conditions – are well established in clinical tria was ls and supported by NHS guidance. The goal is to maximise those benefits by making sure the weight you lose is predominantly fat, not muscle. That’s exactly what CheqUp is here to help you do.
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References
¹ Jastreboff, A.M., et al. (2022). Tirzepatide once weekly for the treatment of obesity. New England Journal of Medicine, 387(3), 205-216.
² Wilding, J.P.H., et al. (2021). Once-weekly semaglutide in adults with overweight or obesity. New England Journal of Medicine, 384(11), 989-1002.
³ Alawadhi, A.A., et al. (2026). LEAN mass preservation with resistance exercise and protein during semaglutide and tirzepatide therapy (LEAN-PREP study). BMJ Open, 16, e116911.
⁴ NHS. (2026). Menopause: Symptoms. http://nhs.uk/conditions/menopause/symptoms/
⁵ Leeners, B., et al. (2017). Ovarian hormones and obesity. Human Reproduction Update, 23(3), 300-321.
⁶ NHS. (2026). Menopause: Things you can do. https://www.nhs.uk/conditions/menopause/things-you-can-do/
