How to prevent muscle loss on Mounjaro

GLP-1 (glucagon-like peptide-1) is a type of incretin, a gut hormone that helps to regulate your blood sugar levels. GLP-1 receptor agonists, such as tirzepatide (Mounjaro), mimic or boost the effects of this natural hormone to make you feel less hungry. As a result, you eat less and lose weight when taking Mounjaro.

However, not all the weight you lose on Mounjaro is fat. Research indicates that up to one-third of this weight loss is ‘non-fat mass’ – muscle and bone mass (lean mass). Specifically, the SURMOUNT-1 trial, which studied tirzepatide in people living at a higher weight without diabetes, found that participants experienced a:

• 33.9% reduction in fat mass
• 10.9% reduction in lean mass

Of course, some amount of lean mass loss during significant weight loss is both normal and expected. In addition, these results clearly show that the primary weight lost while on weight loss injections comes from fat. However, lean muscle mass is vital for our health.

So, it’s important to take care of your muscle-mass and learn how to avoid muscle loss on Mounjaro.

Why does Mounjaro cause muscle loss?

The biology behind weight loss, fat loss and muscle loss is not clear cut. But we have a relatively good idea why weight loss can lead to muscle loss.

Put simply, whether you gain weight or lose weight comes down to how many calories you take in versus how many you burn. Now, this is a huge oversimplification, especially as all bodies are unique and respond to diet and exercise changes in different ways. But, to keep things simple…

Calories are energy that we get from food. We need to eat because we need energy to live. But if we eat more energy than we can burn, the body stores it as adipose tissue (which is just another word for fat). On the flip side, if we eat less energy than we burn, the body needs to start looking for alternative sources of energy from the energy it already has stored away, in the form of fat and muscle.

So even though it’d be nice if we only lost fat mass when we lose weight, it’s entirely normal to lose some lean mass as well. However, your body is more likely to burn lean mass if you lose weight rapidly.

Importantly, this doesn’t mean that taking Mounjaro is an unhealthy way to lose weight? It just means that it’s important to take steps to prevent muscle loss when you take Mounjaro.

The importance of muscle mass

So, why is it important to preserve muscle mass when you lose weight? Well, muscle plays a vital role in your overall health, helping to:

• Support your metabolism
• Give you energy
• Keep you strong
• Control your blood sugar levels
• Improve your insulin sensitivity
• Reduce your risk of falling over

This means, if you lose weight quickly and burn muscle as well as fat, it can cause:

• Your metabolism to slow down, which can increase your risk of weight regain
• A loss of strength and mobility
• Increased fatigue
• Changes to your posture
• Less resilience to illness or ageing

How to preserve muscle mass on Mounjaro

Recent research found that people can preserve muscle mass while losing weight with GLP-1 medications by eating a protein-rich diet and doing regular resistance training:

Eating a protein-rich diet

Proteins are known as the building blocks of life. They are molecules made of amino acids that your body uses to:

• Help your body grow and repair
• Clear bacteria and viruses from your body
• Break down nutrients in the food you eat
• Send chemical signals throughout your body
• Create the energy your body needs to function
• Transport haemoglobin, which carries oxygen, to your body’s tissues

There are lots of different types of protein, and they all perform different functions in your body. This means you need to eat a variety of different protein sources to get all the amino acids you need to support your health.

Good protein sources include:

• Greek yoghurt
• Eggs
• Fish
• Tofu
• Tempeh
• Quinoa
• Quorn
• Lean meat

Most adults need around 0.75g of protein per kilo of body weight per day. This is around 45g per day for the average woman and 55g per day for the average man. To put that into context, that’s about two portions of meat, fish, nuts or tofu per day. A ‘portion’ of protein should fit into the palm of your hand.

Regular resistance training

Resistance training, or strength training, is any activity that aims to build muscle, including:

• Weight training (weightlifting, barbells, kettlebells, medicine balls)
• Body weight exercises (push-ups, burpees, planks, wall squats, lunges)
• Resistance band exercises
• Pilates

The intention is for your muscles to work against some kind of resistance to make them adapt to the demands you’re putting on them and grow stronger.

To preserve and build your muscle mass, you should aim for two resistance training sessions per week that last between 30 minutes to an hour.

Sources

1. Weight loss: Study finds keys to minimize muscle loss from GLP-1 drugs
2. Weight loss drugs help with fat loss – but they cause bone and muscle loss too - News - University of Liverpool
3. Enhancing GLP-1 Benefits with Protein Intake
4. What Are Proteins? Definition, Types & Examples
5. How Should You Treat Muscle Mass Loss in GLP-1 Patients?
6. Protein: what you need to know - BHF
7. How can I prevent muscle loss when using weight loss medications? | Northwell Health
8. What Is Strength Training and Its Benefits?