Introduction
GLP-1 medications have changed the way many people approach weight loss. They can be highly effective at helping people lose weight, but the number on the scale doesn't tell the whole story.
When you lose weight, your body can lose both fat mass and lean mass. Lean mass includes skeletal muscle, but also other tissues and body components, so a reduction in lean mass does not automatically mean an equivalent loss of muscle.
That distinction matters.
If you're using a GLP-1 medication and want to lose weight while maintaining strength and muscle, resistance training and adequate nutrition deserve a place in your plan.
Maintain is built around those principles.
Why Can Muscle Be Lost During Weight Loss?
When you lose weight, your body has less energy available than it needs to maintain its previous body mass. The resulting weight loss is primarily fat mass, but some lean mass can also be lost.
This isn't unique to GLP-1 medications. Lean mass can decrease during significant weight loss through different approaches, including lifestyle-based weight loss and weight-loss medication.
Recent research has found that lean mass can account for a meaningful proportion of total weight lost during treatment with incretin-based medications. However, the exact proportion varies between medications, studies and individuals.
Importantly, lean mass is not the same thing as muscle mass.
Measurements such as DXA-derived lean mass include more than skeletal muscle. Researchers therefore caution against treating every kilogram of lost lean mass as a kilogram of lost muscle.
The quality of weight loss matters alongside the amount of weight lost.
Why Does Muscle Matter?
Muscle helps you produce force and carry out everyday physical activities.
It contributes to:
- Strength
- Movement and mobility
- Physical function
- Exercise performance
- Maintaining independence as you age
For someone intentionally losing weight, maintaining physical performance can be just as useful to monitor as changes on the scale.
That's why a muscle-focused approach to weight loss isn't simply about trying to make the scale move more slowly or quickly. It's about making strength training, adequate nutrition and physical function part of the overall picture.
Does GLP-1 Medication Automatically Cause Muscle Loss?
No.
It's important not to oversimplify the evidence.
GLP-1 receptor agonists and related incretin-based medications generally produce substantial weight loss, with most of the reduction coming from fat mass. Studies also find reductions in lean mass, but the amount varies considerably and lean-mass measurements should not automatically be interpreted as skeletal-muscle loss.
Recent research also suggests that reductions in lean mass do not necessarily translate into reduced strength or physical function. A 2025 review concluded that GLP-1-associated weight loss is predominantly fat loss, with more modest reductions in lean body mass and no consistent deterioration in strength or function.
So the goal shouldn't be to assume that taking a GLP-1 means you're going to lose muscle.
Instead, it's sensible to actively support muscle and monitor your progress while losing weight.
How Can You Support Muscle During GLP-1 Weight Loss?
Two areas receive particular attention in the research:
1. Resistance training
Resistance training gives your muscles a reason to remain strong and adapt to physical demands.
Reviews of weight-loss treatment involving incretin-based medications consistently identify resistance training as an important strategy for supporting lean mass and physical function.
2. Adequate protein
Getting enough protein can help you meet your nutritional needs while losing weight.
This can be particularly relevant when GLP-1 treatment reduces appetite and makes it harder to eat enough food overall. A joint advisory from major nutrition and obesity organisations notes that adequate protein can be difficult to achieve for some people taking GLP-1 therapies and recommends prioritising protein-rich foods.
Protein shouldn't be viewed in isolation, though. Current guidance emphasises that protein intake alone isn't a substitute for resistance training when the goal is to support lean mass during weight loss.
Resistance Training
You don't need an elaborate bodybuilding programme to start resistance training.
The important thing is to give your muscles regular resistance and gradually challenge them appropriately over time.
Depending on your experience and equipment, that could include:
- Squats
- Presses
- Rows
- Pulldowns
- Lunges
- Hip hinges
- Shoulder presses
- Curls
- Triceps exercises
- Core exercises
The right exercises, training volume and progression will depend on your experience, goals, equipment and individual circumstances.
Consistency matters more than having a perfect programme.
Maintain creates personalised workout plans based on your experience, available equipment and schedule, while letting you record sets, reps and weights so you can see how your training develops.
Protein
Protein is an important part of nutrition during weight loss.
For people taking GLP-1 medications, reduced appetite can sometimes make it difficult to consume enough food — and therefore enough protein — to meet nutritional needs. Expert guidance recommends prioritising protein-rich foods and considering practical, nutrient-dense options when appetite is reduced.
Useful protein sources can include:
- Fish and seafood
- Eggs
- Greek yogurt
- Cottage cheese
- Lean poultry
- Beans and lentils
- Soy and other plant proteins
- Nuts and seeds
- Protein-rich shakes or other fortified foods when appropriate
There isn't one protein target that is right for everyone.
Your requirements can depend on factors such as body size, age, activity level, health status and overall diet. People with certain medical conditions may also need individual advice from a healthcare professional or registered dietitian.
Maintain provides a personalised protein target as part of its nutrition tools, helping you make protein a measurable part of your daily routine.
Track More Than Body Weight
Your weight is useful information, but it isn't the complete picture.
Two people could lose the same amount of weight while experiencing very different changes in body composition, strength, fitness and training performance.
That's why it can be useful to pay attention to several measures over time:
- Body weight
- Look at trends rather than individual daily fluctuations.
- Strength
- Are you maintaining or improving your usual lifts?
- Training consistency
- How consistently are you completing your planned workouts?
- Nutrition
- Are you consistently meeting your protein and overall nutrition targets?
- Progress photos
- Visual changes can provide another way to track progress over time.
No single measurement tells you exactly how much muscle you've gained or lost. More precise body-composition assessment requires appropriate measurement methods and interpretation.
What About Ozempic, Wegovy, Mounjaro and Zepbound?
GLP-1 and GLP-1 medication are often used broadly online, but not all weight-loss medications work in exactly the same way.
Ozempic contains semaglutide.
Wegovy contains semaglutide.
Mounjaro contains tirzepatide.
Zepbound contains tirzepatide.
Semaglutide is a GLP-1 receptor agonist, while tirzepatide acts on both the GIP and GLP-1 receptors.
Research into body composition and lean mass is continuing across these treatments, and results shouldn't automatically be assumed to apply identically to every medication.
Frequently Asked Questions
Can you lose muscle while taking a GLP-1?
You can lose some lean mass during weight loss while taking a GLP-1 medication, but lean mass is not the same thing as skeletal muscle. The amount varies between individuals and studies. Resistance training and adequate nutrition can help support muscle and physical function during weight loss.
How can I maintain muscle while taking a GLP-1?
Regular resistance training and adequate nutrition are two important parts of supporting muscle during weight loss. Tracking your strength, training consistency and protein intake can also help you monitor your progress.
Does protein help maintain muscle during weight loss?
Adequate protein can help support nutritional needs and lean mass during weight loss. However, protein works alongside resistance training rather than replacing it. Individual protein requirements vary.
Is strength training important while taking a GLP-1?
Resistance training gives your muscles a reason to remain strong and adapt to physical demands. It is therefore an important part of a muscle-focused approach to weight loss.
Does losing lean mass always mean losing muscle?
No. Lean mass measurements can include skeletal muscle as well as other tissues and body components. A reduction in measured lean mass should therefore not automatically be interpreted as an equivalent loss of muscle.
Can I build muscle while losing weight?
It is possible for some people to improve strength and potentially gain muscle while losing weight, particularly when resistance training is introduced or improved. Results vary depending on factors such as training experience, nutrition, body composition and individual circumstances.
Should I change my GLP-1 medication because I'm worried about muscle loss?
Do not change, stop or adjust a prescribed medication based on information from Maintain. If you are concerned about muscle loss, nutrition, strength or side effects, discuss your situation with your healthcare professional.
Sources & References
- Research on lean mass and GLP-1-associated weight loss
- Muscle loss during weight loss — mechanisms and context
- Effect of GLP-1 Receptor Agonists at Doses for Obesity Management on Muscle Health
- Strategies for Minimizing Muscle Loss During Use of Incretin-Mimetic Drugs
- Nutritional Priorities to Support GLP-1 Therapy for Obesity
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