How to prevent muscle loss while on Mounjaro

It's no secret that when you start your weight loss journey, your body is going to change. Some of these changes might be obvious — clothes fitting differently, having more energy, or better quality sleep.

But there are also subtle things that happen in the background, like your metabolism or body composition changing.

One part of this equation is muscle mass. Our resident gym girlies might've heard this already, but weight loss can lead to muscle mass loss [1].

It's not all bad news, though. Looking after yourself throughout your weight loss treatment can help you achieve the healthier body composition you're after — without sacrificing those biceps!

What is muscle loss and how does it happen?

Muscle loss can happen with any kind of weight loss [1]. While your body is breaking down fat during the weight loss process, you also tend to lose some lean body mass [2].

Lean mass is also known as the fat-free mass of the body — think water, bone mass, organs, and even muscle.

According to researchers, it's pretty common to lose around 20-40% of lean body mass during your weight loss journey. However, most weight loss methods balance this out, and fat loss is more substantial than lean mass loss [3].

So when does lean mass loss become a problem? Our bodies need energy to function, and they'll find it wherever they can get it (looking at you, soy iced latte).

When you start losing weight, your body will break down fat and other tissues to create energy.

We already know it's impossible to target weight loss to a specific area of the body — we also can't choose where the body draws its energy from [2].  

If you're not eating enough, this fuel source could soon end up being your muscles. This is more likely for people on extreme calorie deficit diets — where you're burning a lot more calories than you're consuming [2].

The end result is muscle atrophy (a thinning or reduction in muscle tissue). This creates problems with strength, and sometimes movement difficulties [2].

One of the biggest risk factors for muscle loss is rapid weight loss [1].

Studies suggest that rather than focusing on dropping weight quickly — and risking the body breaking down lean tissue — we should focus on going slow and making sure we're losing weight in a way that helps maintain a healthy body composition [4].

Can Mounjaro cause muscle loss?

There's definitely been concerns raised about whether Mounjaro causes muscle loss, and research is still pretty limited.

However, a recent study in 2022 showed that people taking Mounjaro lost 3 times more fat mass than lean body mass — meaning their body composition became a lot healthier [5].

The same study suggested that the ratio of fat loss vs. lean mass loss was similar to other weight loss and obesity treatments, e.g. surgery or lifestyle-based interventions [5].

The other important thing to remember here is that being overweight can hurt your muscle quality.

People who are overweight might have more muscle mass, but this doesn't reflect muscle strength or function. Losing weight in a healthy way can actually help to improve muscle strength and quality [6].

Preventing muscle loss while taking Mounjaro

Some loss of muscle mass is normal during your weight loss treatment, but there are lots of ways you can prevent it from becoming a problem. Here are the top ways you can maintain muscle mass even while losing weight:

1. Eat a high-protein diet

Eating enough protein is important for a number of reasons, but during weight loss, it's even more crucial.

Firstly, protein helps you feel fuller for longer after a meal. By balancing your meals with the right amount of protein, healthy fats, and carbohydrates, you'll feel more satisfied and less likely to reach for the snacks [2].

Research shows that adequate protein intake can prevent muscle mass loss.

Protein can help with maintaining muscle mass, muscle growth, recovery from injuries, and preserving muscle strength as we get older [7].

This doesn't mean you need to eat steak for breakfast — you shouldn't overdo it either. Your recommended protein intake will depend on things like your age, activity levels, and health goals.

It's a great idea to chat with your GP or healthcare provider before making any changes to your diet [7].

2. Avoid skipping meals

If you wait too long between meals or don't eat enough throughout your day, it can really affect your metabolism and eating habits [2].

You might not eat until lunch, by which time you're starving. This can cause overeating, eating too fast (leading to bloating and feeling uncomfortable), and messed up digestion [2].

When you skip meals your body also goes into survival mode — trying to hold onto whatever it can as a fuel source. Then, your hormones kick in and start prompting you to seek out more food, while slowing down your metabolism [2].

Finally, as we mentioned earlier, if you're not eating enough food your body will find the next energy source it can — breaking down your muscles for fuel instead. This is why getting the right nutrition can do a lot to prevent loss of muscle mass [2].

We know meal planning and figuring out what the weight loss journey should look like can be a challenge.

The good news is you don't have to do it all on your own. Our team of coaches and health experts are here to guide you and make sure you have a plan tailored to your body's needs.

3. Add strength training to your routine

One of the most important parts of any healthy weight loss journey (as much as we sometimes hate to admit it) is exercise. Luckily, exercise doesn't always have to be boring or torturous — it's more about finding a way to move your body that you enjoy.

Whether you're a pilates powerhouse, or someone who enjoys a nice walk around the neighbourhood, you've probably heard that exercise can help preserve muscle mass.

The research definitely backs this up: studies show that exercise improves your insulin sensitivity and helps with muscle protein synthesis. In simple terms, this means it regulates your metabolism and helps with muscle growth [6].

Research shows that strength training and regular resistance training in particular can really go a long way in maintaining healthy muscle mass.

It works to counteract the muscle loss process but also has added bonuses of improved strength, flexibility, bone density, and even better sleep [7].

4. Take time to recover

It sounds counterintuitive, but your muscles actually need to rest between workouts to get the maximum benefit.

They need time to repair themselves and grow — without adequate rest, you'll undo everything you worked hard for [7].

Make sure you pace yourself with your exercise routine, especially if you're a beginner. And if you're unsure about what that routine should look like, check in with your coach or GP.

5. Get enough sleep

Getting enough sleep each night is absolutely vital to healthy weight loss. Sleep regulates your hunger hormones and metabolism, and even impacts the type of food you crave [8].

A study involving children and adolescents showed that lack of sleep was linked to decreased metabolic rate, and increased intake of sweet, salty, fatty, and starchy foods [8].

In adults, sleep deprivation can cause glucose intolerance and insulin resistance. All of these factors can lead to weight gain, and make it harder to engage in physical activity that helps maintain muscle [8].

Try to aim for at least 7 hours of sleep per night (8 or 9 hours if you can get it!).

And, you've heard it before, but putting the phone down and going to bed at the same time each night can really help you get the most out of your sleep routine [8].

6. Don't rush the weight loss process

You might feel really motivated to lose weight and want to see results as quickly as possible, but faster isn't better when it comes to your health. We know that if you're rapidly losing weight, you're more likely to experience lean mass loss, reduced bone density, and other complications [2].

So start slow, and don't introduce any extreme calorie deficits or diets. You can focus on making small, sustainable changes like [9]:

• Getting the right nutrition (eating a range of foods, lots of fruit and veg!)
• Finding enjoyable ways to move your body
• Limiting 'occassional' food like lollies, chocolate, and snack foods
• Reducing alcohol intake
• Drinking more water
• Eating at regular times throughout the day, and having a healthy snack between meals if you need to.

If you're on weight loss medication and you're dropping body weight very quickly, it might be time to check in with your care team about your dose and how to manage this.

Sometimes things like side effects can make it hard to eat a balanced diet, or you might need to reduce your dose for a little while to help prevent muscle loss. Luckily, we're here to support you and figure out the best approach for your body.

The less you rush the process, the more you'll be able to meet your goals and keep the weight off in a sustainable way.

Mounjaro muscle loss might happen — but if you use the above strategies and check in regularly with your healthcare provider, you can prevent it from being a problem.

Juniper’s Weight Reset Programme gives you everything you need to reach your goals.

The programme combines weight loss drugs (including Mounjaro) to encourage weight loss, hands-on support from a team of health experts, including clinicians, dietitians and health coaches, and access to an app where you can track your progress.

If you have concerns about side effects, like muscle loss, our clinicians are there to address any questions you might have.