June 4, 2026, 1:16 pm | Read time: 6 minutes
For years, scientists have been searching for new ways to reduce the risk of breast cancer. Now, medications originally developed for type 2 diabetes and now known primarily as weight loss injections are coming into focus. In a large U.S. study, researchers examined whether there is a connection between GLP-1 medications and breast cancer, and they arrived at surprising results.
More Than 111,000 Women Studied
The current study from the University of Pennsylvania is an observational study. The researchers analyzed existing electronic health data to investigate which women developed breast cancer during the study period.1
More than 111,000 women between the ages of 45 and 80 with overweight or obesity (BMI of at least 25) were studied. They had received a breast examination between 2022 and 2025 and were on average 61 years old.
BMI: When Is It Considered Overweight?
The Body Mass Index (BMI) relates body weight to height and serves as a rough guide for body weight.2
Under 18.5: Underweight
18.5 to 24.9: Normal weight
25 to 29.9: Overweight
30 to 34.9: Obesity Grade I
35 to 39.9: Obesity Grade II
40 or higher: Obesity Grade III
For the current study, only women with a BMI of at least 25 were included. Therefore, the results do not automatically apply to women with normal weight.
Of these, 15,264 women had been prescribed a GLP-1 medication before their breast examination. The remaining 96,382 women had no documented GLP-1 treatment.
To improve comparability, the researchers also assembled two as similar as possible groups. They considered factors such as age, body weight, breast density, ethnic background, and type 2 diabetes. After this adjustment, 30,528 women were available for further analysis.
Also of interest: Breast Cancer–Risk Constellations Where a Genetic Test Is Recommended
Less Breast Cancer With GLP-1 Medications
During the study period, breast cancer was diagnosed in 2,628 of the 111,646 women. This corresponds to about two out of 100 women.
In the group with GLP-1 treatment, breast cancer was diagnosed in just under two out of 100 women. Without these medications, it was about 2.5 out of 100 women. In other words, women who received a GLP-1 medication were diagnosed with breast cancer slightly less often in this study than comparable women without this treatment.
Even after a direct comparison of as similar as possible women, this connection remained. The researchers considered factors such as age, body weight, breast density, and diabetes. Even then, breast cancer was diagnosed less frequently in the GLP-1 group than in the comparison group.
Similar connections were observed in both women with and without type 2 diabetes, as well as in Black and white women.
What the Results Mean for Women
The results provide a new indication that GLP-1 medications may be associated with additional health effects beyond weight loss and improved blood sugar control. Since overweight is a significant risk factor for breast cancer, research has been interested for years in whether effective weight loss therapies could also influence cancer development.
Particularly noteworthy is the size of the study. With more than 111,000 women and 2,628 breast cancer cases, it is one of the largest studies to specifically investigate this connection. Additionally, only women who had received a breast examination were analyzed. This allowed differences in early cancer detection to be at least partially considered.
For women, this does not mean that GLP-1 medications can already be recommended for breast cancer prevention. The study only shows a connection between medication intake and a lower breast cancer rate. Whether the drugs themselves are responsible remains open.
The authors therefore see their results as an important starting point for further investigations to clarify whether a protective effect actually exists.
New Google Feature! How to Select FITBOOK as a Preferred Source
Important Questions the Study Answers
The results may also be interesting because they address frequently discussed questions about GLP-1 medications. On the one hand, it was previously unclear whether a possible connection with a lower breast cancer rate occurs only in women with type 2 diabetes. In the current study, however, the connection was shown in both women with and without diabetes.
On the other hand, it is often assumed that the possible benefits of GLP-1 medications are solely due to weight loss. However, the current data provide an interesting indication against this: The lower breast cancer risk persisted even when the researchers considered weight loss in their analyses. This suggests that a possible protective effect cannot be explained by less body weight alone.
The authors refer to laboratory and animal studies that suggest further explanations. According to these, GLP-1 medications could directly influence biological processes that play a role in cancer development. Anti-inflammatory effects and changes in metabolic processes in cancer cells are among the topics discussed. However, whether such mechanisms can actually slow tumor growth in humans is not yet clarified.
What Previous Studies Show
Overweight is one of the most important modifiable risk factors for breast cancer, especially after menopause. At the same time, GLP-1 receptor agonists are increasingly used to treat type 2 diabetes and for weight reduction.3
In addition to their known effects on weight and blood sugar, there are indications that these medications could also influence biological processes involved in cancer development.4 However, whether this actually affects breast cancer risk has so far been unclear. Previous studies have provided conflicting results.5
Researchers at the University of Pennsylvania therefore investigated whether women with overweight or obesity under GLP-1 therapy develop breast cancer more or less frequently than comparable women without such treatment.
Causes, Symptoms and Consequences of Obesity
Type 2 Diabetes Increases the Risk of Several Types of Cancer – Men Particularly Affected
What the Study Cannot Answer
No Proof of a Protective Effect
Despite the striking results, the study has important limitations. As it is an observational study, it cannot prove a cause-and-effect relationship. The researchers cannot demonstrate that the medications were directly responsible for the lower breast cancer rate.
Not All Influencing Factors Can Be Excluded
Although important factors such as age, body weight, breast density, ethnic background, and diabetes were considered, unknown differences between the groups could have influenced the result.
Open Questions About Duration and Dosage
Additionally, the study did not examine how long the women had taken the medications or what dosages were used. Various GLP-1 agents were also evaluated together. Therefore, it remains unclear whether certain preparations or longer intake periods could show stronger effects.
Why Further Studies Are Needed Now
The authors therefore emphasize that their results primarily provide new hypotheses. Only clinical studies, in which participants are randomly assigned to different treatments, can clarify whether GLP-1 medications actually reduce breast cancer risk.
Conclusion: Promising, but Not Proven
In this large U.S. study with 111,646 women, the use of GLP-1 medications was associated with a lower breast cancer rate. Women with a documented GLP-1 treatment were less frequently diagnosed with breast cancer than comparable women without these medications.
The results are scientifically interesting and provide an important clue for further research. However, they do not prove that GLP-1 medications prevent breast cancer. Targeted clinical studies are necessary to answer this question.