For decades, doctors have known that maintaining a healthy weight can lower the risk of many serious diseases.
Excess body weight has been linked to heart disease, type 2 diabetes, high blood pressure, and several forms of cancer.
Among women, carrying extra weight after menopause is considered one of the most important risk factors for breast cancer.
Because of this connection, researchers have become increasingly interested in medications that help people lose weight. One group of drugs attracting enormous attention is known as GLP-1 medications. These include Ozempic, Wegovy, Mounjaro, and Zepbound, which have become some of the most widely prescribed weight-loss medicines in recent years.
A new study suggests these drugs may offer benefits beyond weight management. Researchers found that women using GLP-1 medications appeared to develop breast cancer less often than women who were not taking the drugs.
The study was presented at the 2026 American Society of Clinical Oncology Annual Meeting and published in JCO Oncology Practice. The research was led by scientists from the University of Pennsylvania Perelman School of Medicine.
Breast cancer is one of the most frequently diagnosed cancers among women. Although treatment outcomes have improved significantly, prevention remains a major goal. Doctors encourage healthy lifestyles, regular screening, and risk-reduction strategies, but there are relatively few proven methods for preventing breast cancer in women who are at increased risk.
The researchers examined medical records from more than 111,000 women aged 45 to 80. All participants had a body mass index of at least 25 and had received breast imaging through the Penn Medicine health system.
More than 15,000 women had used GLP-1 medications, while over 96,000 had not. The researchers compared how often breast cancer was diagnosed in each group.
Because studies like this can be influenced by differences between participants, the team also created a carefully matched comparison group. Each woman using a GLP-1 medication was paired with a similar woman who did not use the drugs. The matching process considered factors such as age, body weight, diabetes status, race, ethnicity, and breast density.
The researchers found a remarkably similar pattern in both analyses. Women taking GLP-1 medications were about one-third less likely to develop breast cancer than nonusers.
This finding is particularly interesting because the medications were never designed as cancer treatments. They were originally developed to help control blood sugar levels in people with type 2 diabetes. Later, doctors discovered that they could also produce substantial weight loss, leading to their widespread use for obesity treatment.
Scientists believe there are several possible reasons for the observed reduction in breast cancer risk. One explanation involves weight loss itself. Fat tissue is biologically active and can influence hormone levels, inflammation, and other processes that affect cancer development. Losing excess weight may help reduce some of these risks.
Another possibility is that GLP-1 medications directly affect biological pathways involved in cancer growth. Research has shown that these drugs can reduce inflammation, improve metabolic health, and influence cellular signaling systems. Some researchers suspect these effects could help create a less favorable environment for cancer to develop.
Despite the encouraging findings, experts urge caution. The study does not prove that the medications prevented breast cancer. Observational studies can identify patterns, but they cannot establish direct cause and effect.
There are also important questions that remain unanswered. The researchers did not determine whether one specific medication performed better than another. They also did not evaluate how long women had taken the medications or whether the effects differed according to genetic risk factors or tumor characteristics.
To answer these questions, the University of Pennsylvania team is preparing larger prospective clinical trials. These studies will follow participants over time and may provide stronger evidence about whether GLP-1 medications truly reduce breast cancer risk.
If future trials confirm the findings, the impact could be significant. Unlike some existing prevention options, GLP-1 medications are already familiar to doctors and widely used by patients. This could make them a practical option for breast cancer prevention in selected high-risk groups.
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