Why Maintaining Muscle Matters During Medicated Weight Loss
Posted on August 7, 2026 by Sally-Anne Turner
Beyond the Scales
Weight loss using GLP-1s isn't just for the ladies.
A study that was conducted by the Health Survey for England in 2024 found that as many as 70% of men in the UK are overweight, versus 62% of women. It also noted that overall, men were more likely to be overweight and obese than women.
You may have tried the weight loss patches. And the exercise routines. So, if you now want to try to lose weight with oral or injectable weight loss, it's important to know how to do it safely and how to avoid side effects. However, one of the most common queries men have about weight loss medication is related to muscle mass. If you use a GLP-1, will it cause you to lose muscle?
It's a relevant question, and it's one that our team at the Bodyline Clinic are familiar with. Our clinical team have helped over 100,000 people to hit their weight loss targets successfully, without sacrificing their health or muscle mass. We personalise our clinical care for each person and provide individualised diet plans and exercise regimens to help each of our patients reach their full potential.
So, do these medications cause muscle loss, and how can that be prevented?
Do You Lose Muscle Mass on GLP-1s?
Can you lose muscle mass when taking GLP-1 medications? In short, yes.
Why does this happen? It is usually linked to diet. Specifically, as these medications suppress appetite, it can lead people who take them to consume less protein. This caloric deficit can lead to muscle breakdown and other conditions, like sarcopenia, which is usually found in older people and is a part of the natural ageing process. This is why if you are an older person who wants to use GLP-1s as part of your weight loss journey, you will need clinical help to do this safely. See our piece on how we support elderly weight loss at the Bodyline Clinic here.
Mounjaro vs Wegovy and Muscle Loss
Another question you may have when starting GLP-1s is: do the different medications produce different levels of muscle mass loss?
Interestingly, yes, they do. We should note here that both Ozempic and Wegovy have the same active ingredient (semaglutide); we can assume that there may be similarities in lean mass loss or muscle over both treatments. Of course, Ozempic is prescribed at lower doses and to different patient groups. When looking at Wegovy vs Mounjaro, we see some interesting differences.
Wegovy
The STEP 1 Trial highlighted that people who were overweight or obese who took Wegovy 2.4mg (injectables, not Wegovy tablets UK) over 68 weeks lost 9.7% lean body mass from baseline. This was measured using DXA scans. The approximate proportion of weight lost from lean mass was calculated to be between 25–35% based on measurements.
Mounjaro
The SURMOUNT-1 DXA Substudy noted that people who were diagnosed as overweight and took Mounjaro for 72 weeks (versus a placebo) lost approximately 10.9% of their muscle compared to baseline. When overall weight loss was calculated, it was approximately 25% of the total weight loss. This was also measured using DXA scans.
Looking at the muscle loss percentages of those two GLP-1s, how does it compare to regular weight loss options, such as exercise and dieting? Let's look at a group who regularly undergo weight loss (and often muscle loss) as part of their athletic training: bodybuilders.
At this point in time, there is no study that directly compares muscle mass loss on medications like Ozempic to lean muscle loss in professional bodybuilders. What we do have are statistics from clinical studies that look at both. GLP-1 medications result in around 20–30% of weight lost coming from lean mass, with most loss still being fat — better than many people fear. Bodybuilders in contest prep typically lose 15–25% lean mass when protein and resistance training are maintained, with often very good muscle preservation despite aggressive dieting. Complete water fasting can see over 40–50% of early weight lost as lean tissue, with poor preservation unless fasting is short-term.
It is easy to look at this comparison and panic. However, it should be noted that when someone is experiencing GLP-1 lean mass loss, it is likely due to adaptation — it is not pathological wastage of muscle, which can be seen in many long-term bodybuilders. A study from 2026 in Cell Reports Medicine noted that while muscle mass decreased slightly during GLP-1 treatments, participants maintained muscle strength and function overall. There was also a noted decrease in water retained in the body and in the organs, which added to the loss of weight in general.
Who is at Highest Risk of Losing Muscle?
Even though no two people who undertake GLP-1-based weight loss are the same, certain groups are at a higher risk of losing muscle during these treatments.
- Older adults: People who are over the age of 65 are already at risk of having a decline in muscle. This is called sarcopenia, and any drops in muscle mass or weight can make an older person frailer and at a higher risk of falls.
- Sedentary people: Those who don't engage in resistance or strength training are more likely to lose weight faster. This is because they are not engaging in the required stimulus needed to preserve muscle tissue.
- People with suppressed appetite: This is tricky, as a core side effect of weight loss medication is appetite suppression. However, if you take these medications and do not eat enough protein, your body will break down muscle for energy.
- People who have lost weight quickly: If you have lost body weight quickly with GLP-1s, you are more likely to lose lean tissue compared to those who have lost weight gradually. This is why medical check-ups are vital to health during this process.
At the time of writing, there is no specific GLP-1 diet that increases protein, helps those taking GLP-1s to lose weight and maintain muscle mass. However, for those who are undertaking weight loss later in life, or those who are experiencing more extreme side effects of the weight loss medications, clinical input and monitoring are a must. This will ensure you stay healthy and will help you to lose weight effectively, provided you are attending a legitimate weight loss clinic like the Bodyline Clinic.
Protecting Muscle Mass
It's not all clinical though! There are things you can do at home and in daily life that can help you to keep hold of your muscle.
According to guidelines from both the NHS and Bupa, the best diet to help protect your muscle mass includes:
- Small meals: Eat small meals to help delay stomach emptying and stop eating when you feel full.
- High protein priority: Try to include around 20–30g of protein in each meal, such as lean meats, fish, eggs or tofu. This will help maintain body weight while helping you lose fat.
- Up your fibre: Try to eat vegetables, fruit and wholegrains. This will help digestion and prevent the side effect of constipation that can occur with GLP-1s.
- Stay hydrated: Drink around 1.5–2 litres of water and sugar-free fluid through the day to keep hydration up. You can also integrate low-sugar weight loss shakes if your blood sugar is affected by the GLP-1s.
Now, onto a suitable exercise regime to help you maintain muscle. When you are taking GLP-1s, you should aim to increase your exercise using the following tips from Bupa and the NHS Digital Weight Management Programme as guidance. If you aren't sure about where to start, talk to your prescriber.
- Resistance training: These are great for helping maintain muscle. Aim to complete two to three sessions per week for around 20 to 30 minutes. Focus on bodyweight moves, resistance bands or free weights.
- Aerobic exercise: Try to fit in around 150 minutes of moderate-intensity cardio weekly. This can look like swimming, brisk walking, or even cycling. All of these will help to support your heart health, build up stamina, and, of course, help you maintain muscle mass.
- Balance and flexibility: Interestingly, with all of that additional exercise, you may find that your joints become a bit sore. This is why many clinicians also recommend integrating yoga, stretching, or balance drills into your new exercise regimen. These will help to protect your joints and improve stability, whilst also helping you manage the daily stresses of life.
How is Muscle Monitored During GLP-1 Treatment?
Another thing to note if you want to preserve muscle while taking GLP-1s is that you cannot use the scales alone to accurately assess whether you are losing fat or muscle.
When you begin undertaking oral or injectable weight loss treatments, the clinical team who are overseeing your care should also be checking for any signs of muscle loss.
DXA Scanners
Standing for Dual-energy X-ray Absorptiometry, these are commonly part of the equipment at gyms and in hospitals. They were originally developed to measure bone density but can also measure overall body composition, which can more accurately identify fat mass, lean mass (which includes skeletal muscle, organs, connective tissue and body water), and bone mineral content. DXA scanners can also highlight where fat is distributed through the body, which is ideal if you are also aiming to undertake resistance training or an exercise regimen to increase toning.
Multi-frequency Bioelectrical Impedance
A multi-frequency bioelectrical impedance analysis (MF-BIA) sends safe electrical currents through the body in different frequencies. Water-rich tissues conduct electricity differently from fat. So, the device can accurately estimate total body water, fat, and lean mass (including muscle) to track changes over time and to see whether you are losing fat or muscle as part of your weight loss.
Tape Measurements and Scales
This is pretty baseline, but it can be better than nothing. It allows your clinicians to track weight loss across your waist, hips, mid-section and arm circumference. Best of all, you can track this yourself at home, and your weight can help you to track your BMI.
Monitoring with the Bodyline Clinic
Do you want to lose weight but have concerns about how it may impact your overall health? At the Bodyline Clinic, we offer tailored support for each person who comes to us for medicated weight loss. Our clinical team work with you to ensure that your weight loss journey is effective and safe, helping you to reach your weight loss goals without putting your health at risk.
If you want to know more about what we offer, contact our team today for a free consultation.
FAQs
Do You Lose Muscle on GLP-1s?
The research shows that if you take GLP-1s and are not on a diet that is high in protein, then you are at a higher risk of losing muscle. Exercise is also important for maintaining muscle on a GLP-1 weight loss journey, as is clinical oversight.
Who Is the Most Likely to Lose Muscle During Treatment?
Research has found that older people (those over 65), people who don't engage in resistance or strength training, those who have suppressed appetites and those who have lost weight quickly are the most likely to lose muscle mass during treatment. This is why clinical checks and maintenance need to be a core part of this process.
What Can Prevent Muscle Loss?
Maintaining a healthy diet that is high in protein can help prevent muscle mass loss when taking GLP-1 medications. Also, engaging in resistance training, aerobic exercise, and even adding a bit of yoga into your weekly routine has been shown to help maintain muscle mass while also assisting in weight loss.
