September 21, 2026, 11:44 am | Read time: 5 minutes
GLP-1 receptor agonists are now being used as so-called weight loss injections for people with obesity without metabolic disease–originally, they were developed for the treatment of diabetes. A new study from Germany now shows a potentially unwanted effect of these drugs. According to the study, diabetics treated with a GLP-1 medication also experienced a greater loss of skeletal muscle volume compared to similar individuals without the treatment. However, the results are still preliminary.
How GLP-1 Receptor Agonists Support Weight Loss
GLP-1 receptor agonists mimic the effect of the body’s own hormone GLP-1. This gut hormone is released after eating and influences insulin secretion as well as the feeling of satiety. The medications are therefore used to treat diabetes and can also support weight loss. This group of drugs includes medications commonly referred to as weight loss injections.
Loss of Muscle Mass Due to Weight Loss Injection?
When losing weight, it’s possible that lost pounds can also come from muscle mass if not specifically counteracted. One way to reduce fat while preserving as much muscle mass as possible is through a combination of intermittent fasting and targeted training.1 But what happens when weight is lost using the weight loss injection?
The authors of the current study wanted to find out if weight loss following such treatment might be associated with a greater loss of skeletal muscle.2 The skeletal muscles consist of about 600 individual muscles. These are connected to bones via tendons and enable movement and a stable posture, among other things.
It should be noted at this point that the study has so far only been published on a preprint server. A review by independent experts is still pending.
Study Details
For the study, the researchers used data from the NAKO Health Study.3 NAKO stands for National Cohort, which is the largest epidemiological long-term population study in Germany.
The researchers analyzed data from 58 adults with diabetes who had started using a GLP-1 receptor agonist between two whole-body MRI scans. The interval between the two scans was 4.6 years. For comparison, 130 individuals with diabetes who had never received a GLP-1 medication were used. The comparison subjects were matched by gender, age, body mass index (BMI), and the interval between the scans.
Using the MRI images, the researchers examined how the volume of different tissues changed during the study period. This included various types of fat tissue and, in particular, skeletal muscle. The tissue analysis was conducted using a deep learning method that can recognize and differentiate various tissues in medical images through artificial intelligence. Additionally, the researchers compared changes in body weight between the two groups.
Results: More Muscle Loss in the Weight Loss Injection Group
Participants who started using a GLP-1 medication between MRI scans lost more skeletal muscle volume than those in the comparison group without the treatment. The difference between the two groups was 2.75 percentage points. This difference was statistically significant, the authors write. This means that, according to the statistical criteria of the study, there is little to suggest that it arose by chance alone.
Body weight also decreased more in the group with the GLP-1 medication. The difference between the two groups was 2.54 percentage points and was also statistically significant.
No Significantly Higher Fat Loss with GLP-1 Medication
However, there was no statistically clear difference in fat tissue. The fat tissue inside the torso was 4.8 percent more altered in the group with GLP-1 medications, and the subcutaneous fat tissue by 3.2 percent.
The authors summarize their findings by stating that participants with GLP-1 medications lost about 60 percent more muscle than those in the comparison group. The study thus provides an indication that the weight loss associated with GLP-1 medications is at least partially accompanied by a loss of skeletal muscle volume.
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Possible Significance of the Study
If the so-called weight loss injection also reduces skeletal muscle volume, this would be quite relevant. For assessing weight loss, it’s not only important how many pounds someone loses but also which body tissues are reduced. Skeletal muscles play an important role in movement and posture, among other things.
The observations may raise an important research question: How can people with diabetes (using the weight loss injection) lose as much fat as possible while retaining as much muscle mass as possible?
Whether the observed greater muscle loss also occurs in people without diabetes who are treated with the weight loss injection cannot be answered by this study. Studies with appropriate participants would be necessary for that.
Limitations
This is not a randomized study: Participants were not randomly assigned to a treatment or untreated group. Therefore, the study cannot definitively show that the GLP-1 medications themselves caused the greater muscle loss. Other differences between the groups could also have played a role.
Interpretation is also complicated by the relatively long period of 4.6 years between the MRI scans. During this time, numerous factors could have influenced body weight and muscle mass. For example, the available information does not indicate whether and to what extent the study participants were physically active, how they ate, and so on.
Additionally, the relatively small group of 58 participants who started using a GLP-1 medication is a factor. Whether the results can be generalized to other people with diabetes–let alone to people without diabetes, who were not considered in the study–remains open. Finally, the work is currently only available as a preprint. As long as it has not been reviewed by independent experts, the results should be considered preliminary.
Nevertheless, it provides intriguing insights into what weight loss medications do to fat and muscle in the bodies of diabetics. It seems worthwhile for research to delve deeper into this.