GLP-1s have taken the fitness and health industry by storm. It's proving to be the most powerful weight loss tool in history, with thousands of individuals using some form: Ozempic, WeGovy, or Mounjaro.
However, one side effect has become abundantly clear: excessive muscle loss. Some people want to argue about whether you really lose more muscle than during normal weight loss.
This misses the point because muscle loss is never good, whether you're on a GLP-1 or not. The good thing is we know exactly how to significantly preserve muscle loss, and possibly even build muscle.
Key Points You Need To Know!
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What Is A GLP-1?
A GLP-1 refers to a class of medications that mimics the naturally occurring hormone Glucagon-like peptide-1. Under normal conditions, GLP-1 is naturally released into the body after eating.
After binding to GLP-1 receptors, a cascade of reactions occurs:
- Insulin is released to lower blood sugar
- Slower gastric emptying
- Satiety increased
GLP-1 medications do the same thing; however, they've been modified to resist degradation and maintain these effects for longer periods of time (Holst, 2024).
Keep in mind that different GLP-1 drugs act slightly differently. But for this article, the important part is the end effect; GLP-1 therapies decrease hunger and cravings, resulting in fewer calories eaten and weight loss.
However, some studies have suggested this weight loss includes a high percentage of muscle.
Why Do You Lose Muscle Mass When Taking GLP-1s?
Muscle loss while using a GLP-1 comes from being in an extreme caloric deficit with no resistance training. This is important to understand, as there's no special mechanism in a GLP-1 that causes you to lose muscle mass.
Therefore, a more accurate question is: why does an extreme caloric deficit cause muscle loss?
The good thing is we have a pretty good understanding. Your body can only draw energy from three sources:
- Glycogen is stored in your muscles. This is largely associated with "carbs".
- Fatty acids are stored in your adipose tissue
- Amino acids that build your muscles, i.e., protein
When in a caloric surplus, your body can pull energy from your stored glucose and fatty acids. However, during times of elevated energy needs, your body only has one other place to get energy from.
Your muscles must be broken down to release amino acids that can be used to generate more energy.
This is why guidelines for fat loss suggest a small caloric deficit of 300-500 calories for most people.
How Can You Preserve Or Build Muscle?
Since muscle loss is caused by a caloric deficit, in this sense, there's really no difference between preserving muscle during a normal caloric deficit. Apart from minimizing the deficit, there are three things you can do:
- Follow a resistance training program
- Increase protein intake
- Ensure you get quality sleep
Resistance Training Is Essential For Muscle Health
Resistance training is probably the greatest tool you have to preserve muscle mass while using a GLP-1 (Lahav et al., 2026). Numerous studies have shown that the difference in muscle loss during caloric deficits is significantly smaller when resistance training is involved.
The program doesn't need to be complicated, but should follow some simple guidelines:
- Use compound exercises to train the whole body
- Your program should be progressive in nature. This means you add weight and work as your progress.
- A wide rep range can be used (4-15), but ideally, you use at least some exercises with loads of 80-85% 1RM
Higher Protein Intake Can Preserve Muscle Mass
Increasing protein intake has proven to be another crucial factor in preserving muscle mass while in a deficit. Large meta-analyses have clearly shown that during weight loss, increasing one's protein intake helps preserve muscle mass (Kokura et al., 2024).
Aim to eat at least 1.6g per kilogram of body weight, but eating 2.0 - 2.5g/kg could yield superior results.
Adequate Sleep And Fat Loss
An often overlooked factor for preserving muscle mass is getting adequate sleep. Researchers aren't exactly sure of the mechanisms, but sleep deprivation has a dramatic effect on muscle breakdown.
Research has shown that getting just 5.5 - 6 hours of sleep while in a caloric deficit increases the proportion of muscle loss in total weight loss (Nedeltcheva et al., 2010).
In other words, lacking sleep seems to put your body in a catabolic state, and under the same caloric deficit, your body burns more muscle.
FAQ: How To Preserve And Build Muscle Mass On GLP-1
1. Can you build muscle while taking a GLP-1?
Yes, it is possible to build muscle while taking a GLP-1, although it depends on your calorie intake and training status.
Beginners, individuals returning to training, and those with higher body fat may be able to gain muscle despite losing weight. Progressive resistance training, adequate protein intake, and sufficient recovery are essential.
2. Do GLP-1 medications cause muscle loss?
GLP-1 medications do not directly cause muscle loss. Muscle loss primarily occurs because the reduced appetite created by GLP-1s often leads to a large calorie deficit, especially when combined with inadequate protein intake and little or no resistance training. The same muscle loss can occur during any aggressive weight-loss diet.
3. How much protein should you eat while taking a GLP-1?
Most people taking a GLP-1 should consume at least 1.6 g of protein per kilogram of body weight per day.
During weight loss, increasing protein intake to around 2.0-2.5 g/kg/day may provide additional benefits for preserving lean muscle mass. Distributing protein across multiple meals may also help maximize muscle protein synthesis.
4. What is the best exercise while taking a GLP-1?
Resistance training is the best type of exercise for preserving muscle while taking GLP-1. Focus on a progressive strength-training program built around compound exercises performed at least 2-3 times per week.
Adding regular walking or other aerobic exercise can further support overall health and weight loss.
5. How can you prevent muscle loss while taking Ozempic, Wegovy, or Mounjaro?
The best way to prevent muscle loss while taking a GLP-1 is to combine resistance training, a high-protein diet, and adequate sleep.
Avoid excessively large calorie deficits whenever possible, and continue progressively challenging your muscles throughout your weight-loss journey. Together, these strategies can significantly reduce the amount of muscle lost while dieting.
Recap: How To Preserve Muscle Mass While Using A GLP-1
As you can see, preserving muscle mass while using a GLP-1 is exactly the same as when losing weight without one. The primary mechanism that promotes muscle catabolism is a calorie deficit, so counteracting those effects is the same. Resistance training, increase protein, and get plenty of sleep.
Reference
- Holst, J. J. (2024). GLP-1 physiology in obesity and development of incretin-based drugs for chronic weight management. Nature Metabolism, 6(10), 1866–1885. https://doi.org/10.1038/s42255-024-01113-9
- Kokura, Y., Ueshima, J., Saino, Y., & Maeda, K. (2024). Enhanced protein intake on maintaining muscle mass, strength, and physical function in adults with overweight/obesity: A systematic review and meta-analysis. Clinical nutrition ESPEN, 63, 417–426. https://doi.org/10.1016/j.clnesp.2024.06.030
- Lahav, Y., Yavetz, R., & Gepner, Y. (2026). Resistance training as a key strategy for high-quality weight loss in men and women. Frontiers in endocrinology, 16, 1725500. https://bit.ly/4yJNDww
- Nedeltcheva, A. V., Kilkus, J. M., Imperial, J., Schoeller, D. A., & Penev, P. D. (2010). Insufficient sleep undermines dietary efforts to reduce adiposity. Annals of internal medicine, 153(7), 435–441. https://doi.org/10.7326/0003-4819-153-7-201010050-00006
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