A Large Study Links GLP-1 Use to a 35% Lower Risk of Developing Breast Cancer

Reported by Women's Health Magazine.

The list of conditions GLP-1 medications may quietly work against keeps growing — and the latest addition is significant. A large new analysis published in JCO Oncology Practice, according to Women's Health Magazine, found that women taking GLP-1 drugs like Ozempic or Zepbound had a strikingly lower risk of developing breast cancer than women who weren't on them.

The study pulled health records from nearly 112,000 women aged 45 to 80 with a BMI of 25 or higher who underwent breast imaging between January 2022 and June 2025. Researchers ran two separate analyses — one using the full cohort, and a tighter matched group of 30,528 women paired by age, race, BMI, and other factors. In both, GLP-1 users came out ahead: a 35.1% lower breast cancer risk in the larger group, and 30.5% in the matched cohort. The association held regardless of age, race, ethnicity, BMI, breast density, or diabetes status.

Why the Biology Actually Makes Sense

This isn't a coincidence doctors find shocking. Dr. Gilberto Lopes, chief of Medical Oncology at Sylvester Comprehensive Cancer Center at the University of Miami Health System, points to weight loss as the primary driver. After menopause, fat tissue becomes the body's main estrogen source — and estrogen fuels the most common forms of breast cancer. Shrink the fat, shrink the estrogen supply. GLP-1s also suppress insulin and IGF-1, two signals that can accelerate tumor growth, while dampening the chronic low-grade inflammation that excess weight produces. There's even a more direct mechanism under investigation: some breast tumors carry GLP-1 receptors on their surface, raising the possibility the drugs could act on cancer biology directly. Dr. Elizabeth McDonald, lead study author and professor of Radiology at the Hospital of the University of Pennsylvania, puts it plainly: "GLP-1 agonists reduce weight, and weight alone is a risk factor for breast cancer." For context, research has shown women with obesity face roughly a 30% higher chance of developing breast cancer than those at a so-called normal weight.

What about women who aren't overweight? The evidence doesn't extend there yet, and Dr. Lopes is measured about the prospects: most of the benefit, he says, flows through metabolic correction — less relevant when there's less to correct. As for using GLP-1s purely as a breast cancer prevention tool, he doesn't dismiss it. Tamoxifen already occupies that lane for high-risk women, so the concept isn't new. For now, preventive GLP-1 use would make the most sense where breast cancer risk and a clinical reason for weight loss already overlap — but randomized controlled trials will need to confirm what this observational data is pointing toward.

The research doesn't prove causation, but the signal is consistent enough that it's hard to ignore: the drugs most prescribed for metabolic health may be quietly reshaping cancer risk too.

Read the original at Women's Health Magazine.