Wow. Super interesting study.
For those of you with no attention span, this was a study out of UPenn looking at 111,000 women, median age 61. It did show GLP use lowered breast cancer rates. But it is unclear if this is due to weight loss as the women had a BMI of 25 or more (which weight loss has also been shown to lower breast cancer rates) or something inherent to the GLP. (See a study I blogged about in 2019 which showed a linear reduction in breast cancer risk with weight loss BREAST CANCER WEIGHT).
GLP study showing significant reduction in breast cancer
They start by stating “excess weight is a key modifiable risk factor for breast cancer.” Their study recently published in June 2026 (yes, this is hot off the presses) “GLP 1 Agonists Are Associated with Significant Reduction in Breast Cancer Incidence in Women.”
- Retrospective cohort study Jan 2022-June 2025
- Women ages 45-80, BMI 25 or higher, median age 61.
- Looked for breast cancer detection.
- They also looked at race, ethnicity, age, and Type 2 diabetes
Findings?
Regardless of age, race, ethnicity, BMI, breast density and diabetes, those on GLP 1 treatment had a lower incidence of breast cancer. They estimated 30% lower risk.
Other studies have shown Metformin and Losing Weight lower breast cancer incidence
WEIGHT LOSS
In 2019, I blogged about this on my website. “Sustained Weight Loss and Risk of Breast Cancer in Women 50 Years and Older: A Pooled Analysis of Prospective Data.”
Study:
- 181,000 women. Of these 6930 formed invasive breast cancers during follow up
- Linear risk reduction seen in postmenopausal women (not using HRT)
- They divided the groups into weight loss of 2-4.5kg, 4.5-9kg, and more than 9 kg.
- It had to be sustained loss (not yo-yo ing)
- The weight loss was larger in women with higher BMIs (as expected, as thinner women can’t lose 9kg)
- The 9kg group had a 32% lower risk of breast cancer
METFORMIN
There were multiple studies which came out which indicated metformin use helped reduce breast cancer occurrence. Just to cite two:
Danish study
- Diabetics on insulin or metformin vs control
- Findings: 20% reduction for Type 2 diabetic women with 5 years of metformin use. The strongest inverse association between metformin users and breast cancer was observed among women with diabetes complications. The results did not change appreciably among women without complications
WHI study
Metformin and breast cancer incidence in postmenopausal diabetic women in the Women’s Health Initiative (WHI) came out in 2011. Remember, this was done on postmenopausal diabetic women.
WHI study:
- 156K women of whom 9277 were on medication for diabetes. They were followed for 11 years
- Self reported invasive cancers
- They looked at BMI, physical activity, and HRT
- Findings? Women with diabetes tended to be older, Black, obese, and less physically active. Those on metformin tended to be on it for 1.3 years, where other diabetes medicines were 4.8 years.
- Diabetic women on metformin had 38% fewer ER+/PR+ breast cancers
They conclude, “In diabetic women… this proves support for testing metformin in chemoprevention.”
How can Biohackr Health help?
Clearly there is something real here- losing weight, avoiding diabetes, metformin, GLPs. These are all interconnected. Come in for an evaluation. Is your BMI over 25? Are you pre diabetic? Diabetic? For those populations, intervention clearly helps lower your breast cancer risk. Given that 1 in 8 women get breast cancer (and that rate doubles with dense breasts), this is something to address. We can help you create a plan.
- LOSE WEIGHT. Medical weight loss
- GLPs
- BUILD MUSCLE. Analyze your current status with an InBody scan. Take creatine and NAD. SHOP
- ARE YOU DIABETIC or PREDIABETIC? Test your blood levels. Wear a continuous glucose monitor (CGM) to see what foods spike you and how activity protects you.
It is unclear if you are a normal weight and not diabetic (or prediabetic) that GLPs will help you. But GLPs do interesting things, and the anti inflammatory effect may have an effect. Further testing on normal weight nondiabetic people will let us know.
MEDICAL CITATION
GLP-1 Agonists Are Associated With a Significant Reduction in Breast Cancer Incidence in Women, Journal Clinical Oncology, June 2026
Sustained Weight Loss and Risk of Breast Cancer in Women 50 Years and Older: A Pooled Analysis of Prospective Data, Journal of National Cancer Institute, 2019
Metformin and Incident Breast Cancer among Diabetic Women: A Population-Based Case–Control Study in Denmark, Cancer Epidemiology Biomarkers and Prevention 2011
Metformin and breast cancer incidence in postmenopausal diabetic women in the Women’s Health Initiative (WHI)., Journal of Clinical Oncology 2011