Losing weight doesn’t only mean losing body fat. When your body weight decreases, some of the weight you lose can come from lean mass too.
This can happen with different approaches to weight loss, including while using GLP-1 treatment. The goal isn’t simply to make the number on the scale fall as quickly as possible, but to support fat loss while protecting your muscle, strength and overall health as much as possible.
If you’re using a GLP-1 for weight loss, paying attention to what you eat and how you move can help support your muscle as your weight changes.
Do GLP-1s Cause Muscle Loss?
GLP-1 agonists do not themselves cause loss of muscle mass. However, when in a calorie deficit, whether aided by GLP-1 mediated appetite suppression or not, loss of some muscle mass is possible – and to an extent, normal. The aim during weight loss is therefore to support your body in maintaining as much muscle and strength as possible while reducing excess body fat. With some attention to protein intake and resistance training, it is generally possible to lose significant amounts of weight without extensive loss of muscle mass. In our clinical experience, we have even seen some people increase muscle mass while simultaneously losing fat.
Why Does Protecting Muscle Matter During Weight Loss?
Muscle does much more than affect how your body looks.
Maintaining muscle and strength helps support everyday activities such as walking, lifting and staying active. It also plays an important role in your overall physical health and function.
This is why successful medical weight management shouldn’t be measured by kilograms alone. The quality of the weight you lose matters too.
How Can You Protect Muscle While Taking a GLP-1?
You can’t guarantee that you’ll lose only body fat, but there are practical things you can do to help support your muscle while losing weight.
Eat Enough Protein
Protein provides the building blocks your body needs to maintain and repair muscle.
Because GLP-1 treatment can reduce your appetite and the amount you’re eating, it’s worth making the food you do eat count. Include good sources of protein regularly rather than allowing your overall intake to become too restricted.
Your individual protein needs can vary according to factors such as your starting weight, , fitness goals and what type of exercise you do, so speak to your doctor if you’re unsure how much is appropriate for you. As a general rule, 1.2g protein per kilogram of body weight is sufficient. With a higher BMI, it becomes necessary to use estimated fat-free mass (FFM) in this calculation.
Include Resistance Training
Cardio is useful for your overall health and to assist in creating a calorie deficit, but resistance exercise can be particularly helpful when you’re trying to maintain muscle and strength while losing weight.
That doesn’t mean becoming a bodybuilder or spending every day in the gym. Resistance training simply means asking your muscles to work against resistance, for example through weights, resistance bands or bodyweight exercises.
If you’re new to exercise, have mobility limitations or an existing medical condition, speak to your doctor or an appropriately qualified exercise professional before starting a new programme.
Don’t Focus Only on the Scale
Your body weight can’t tell you whether the weight you’ve lost came from fat, muscle, water or a combination of these.
Pay attention to other signs of progress too, such as:
- Your strength
- How your clothes fit
- Your energy levels and ability to stay active
- Changes in measurements of body composition using an Inbody or DEXA scan
This can give you a more complete picture of your progress than kilograms alone.
Avoid Trying to Lose Weight as Fast as Possible
Faster isn’t always better.
GLP-1 treatment can significantly reduce appetite, but that doesn’t mean eating as little as possible should become the goal. Very restrictive intake can make it harder to meet your protein, vitamin, mineral and overall nutritional needs. An overly aggressive approach to weight loss can also lead to a gaunt, unhealthy appearance and excessive loss of muscle mass. For this reason we generally aim for 500 grams to 1kg loss per week, depending on your individual starting point, medical history and goals. In our clinical experience this results in weight loss that looks, feels and is healthy.
Note that while generally mild and temporary, side effects of GLP-1 treatment such as nausea or other digestive symptoms can also make it more difficult to eat enough or maintain a balanced diet in sensitive individuals. If side effects are affecting your ability to eat or drink normally, speak to your doctor rather than simply trying to push through them.
What if You’re Worried About Losing Muscle?
If you’re taking a GLP-1 and you’re concerned about muscle loss, weakness, your nutritional intake or how quickly you’re losing weight, speak to your doctor.
Your treatment isn’t just about reaching a target number on the scale. Your doctor can consider your progress alongside your overall health, nutrition, physical function and response to treatment.
Where appropriate, your care may also involve support from other healthcare professionals, such as a dietitian or appropriately qualified exercise professional.
GLP-1 Weight Loss Treatment With Meridian Health
At Meridian Health, treatment starts with a medical assessment and online doctor consultation to determine whether GLP-1 treatment may be appropriate and effective for you. Your care continues after treatment begins, allowing your progress and response to be reviewed over time.
Medically reviewed by Dr Joshua Czech, October 2026