A major new study has found that excess body weight is closely linked to an increased risk of breast cancer in postmenopausal women—particularly in those who also develop cardiovascular disease. The research, published in the respected journal CANCER, a peer-reviewed publication of the American Cancer Society, offers new insights into how weight and heart health may work together to influence cancer risk later in life.
While it is already well established that a higher body mass index (BMI) raises the risk of breast cancer in postmenopausal women, scientists have long debated whether this risk varies depending on the presence of other chronic health conditions, such as cardiovascular disease or type 2 diabetes. This new analysis now provides strong evidence that having both a high BMI and cardiovascular disease creates a significantly greater risk than previously understood.
What the Study Found
Researchers from the International Agency for Research on Cancer (IARC), a specialized cancer agency of the World Health Organization, analyzed long-term data from two of Europe’s largest health studies—the European Prospective Investigation into Cancer and Nutrition (EPIC) and the UK Biobank.
The study included 168,547 postmenopausal women who were all free of cardiovascular disease and type 2 diabetes at the start of the study. Researchers tracked the women’s health for a median follow-up period of 10.7 years in EPIC and 10.9 years in the UK Biobank.
Over the course of the study, 6,793 women were diagnosed with breast cancer.
The data revealed a clear and concerning trend:
For every 5 kg/m² increase in BMI, the risk of breast cancer went up by:
31% in women who developed cardiovascular disease during the study period.
13% in women who did not develop cardiovascular disease.
This shows that the link between excess weight and breast cancer is stronger when cardiovascular disease is also present.
What About Type 2 Diabetes?
Interestingly, the study found that type 2 diabetes did not significantly alter the relationship between BMI and breast cancer. Women with or without type 2 diabetes experienced a similar increase in breast cancer risk as BMI increased. This suggests that cardiovascular disease, rather than diabetes, may play a more critical role in amplifying breast cancer risk associated with excess body weight.
Real-World Impact: A Closer Look at the Numbers
To understand the public health implications, researchers calculated how many additional cases of breast cancer would be expected in women with both overweight or obesity (BMI ≥ 25 kg/m²) and cardiovascular disease.
They found that this combination could result in:
153 additional breast cancer cases per 100,000 women per year compared to what would be expected based on population averages.
This highlights a substantial increase in cancer burden tied directly to the dual presence of excess weight and heart disease.
The Intersection of Heart Health and Cancer Risk
This study is one of the first to provide such clear evidence that cardiovascular disease magnifies the cancer risks associated with obesity, specifically in postmenopausal women. Experts suggest that inflammation, hormone imbalances (such as increased estrogen levels from fat tissue), and metabolic disturbances caused by both conditions could contribute to the elevated cancer risk.
According to Dr. Heinz Freisling, the lead researcher from IARC, these findings emphasize the need for preventative strategies targeting weight control and heart health, especially in aging women.
What Women Should Know
This research adds to a growing body of evidence that reinforces the importance of maintaining a healthy weight after menopause—not just to protect the heart, but also to reduce the likelihood of developing breast cancer.
Postmenopausal women, in particular, face unique health risks due to hormonal changes that can influence both fat distribution and disease susceptibility. As estrogen production shifts from the ovaries to fat tissue, excess body fat can lead to higher circulating estrogen levels, which are associated with the development of hormone-sensitive breast cancers.
When cardiovascular disease is also present, this hormonal and metabolic environment may become even more conducive to cancer growth.
Lifestyle and Prevention
The good news is that many of the risks highlighted in this study are modifiable through lifestyle changes:
Healthy diet: Emphasize whole grains, fruits, vegetables, lean proteins, and healthy fats.
Regular physical activity: Aim for at least 150 minutes of moderate exercise per week.
Weight management: Keep BMI within a healthy range (18.5–24.9 kg/m²).
Heart health monitoring: Manage blood pressure, cholesterol, and signs of cardiovascular disease.
Routine screenings: Attend regular mammograms and health checkups, especially after menopause.
Healthcare professionals should also be aware of this connection when coun
