The Connection Between Breast Cancer and Obesity

| October 1, 2021

Christopher D. Still, DO, FACN, FACP, is the Co-clinical Editor of Bariatric Times; Medical Director for the Center for Nutrition and Weight Management, and Director for Geisinger Obesity Research Institute at Geisinger Medical Center in Danville, Pennsylvania.

Dear Colleagues,

As you all are aware, October is breast cancer awareness month, so I thought it was an appropriate time to again discuss obesity’s effect on breast cancer, as well as other cancers. Most importantly, I want to emphasize weight loss, especially surgical weight loss and its effect on cancers. To begin, I would like to acknowledge and congratulate all breast cancer survivors and let patients currently undergoing treatment know that you are all in our thoughts and prayers.

I think we often overlook the significant association with obesity and cancer. Obesity is strongly associated with breast cancer, especially in postmenopausal women, as well as other types of cancers. The International Agency for Research on Cancer has determined, based on epidemiological studies, people with obesity are at increased risk of developing several cancer types, including adenocarcinoma of the esophagus, colon cancer, breast cancer (in postmenopausal women), endometrial cancer, and renal cell cancer. There is also evidence that liver, gallbladder, prostate, and pancreatic cancers are related to obesity as well. Interestingly, there has not been any association between lung cancer and obesity to date.

The driving force for this strong association seems to be insulin resistance (IR). IR develops as a metabolic adaptation to increased levels of circulating free fatty acids released from adipose tissue, especially visceral adipose tissue. In turn, IR produces increased insulin secretion, and this chronic hyperinsulinemia can increase the risk of the above-mentioned cancers—especially colon and endometrial.  In addition to hyperinsulinemia, elevated circulating levels of estrogen, also seen with increased adiposity, has been linked to postmenopausal breast and endometrial cancers, as these are thought to be medicated by increased estrogen levels.

The great news is that weight loss, especially surgical weight loss, had a significant reduction in developing certain types of cancers. In an Annals of Surgery retrospective cohort study of over 22,000 patients who had bariatric surgery and over 66,000 nonsurgical patients, Arterburn et al1 showed bariatric surgery was associated with a lower risk of incident cancer, particularly obesity-associated cancers, such as postmenopausal breast cancer, endometrial cancer, and colon cancer. Moreover, Berger, et al2 in the Annals of Translational Medicine corroborated these findings, again with the biggest benefit on obesity-associated cancers. 

In summary, obesity is strongly associated with many types of cancers. Weight loss, especially surgical weight loss, has been shown to significantly decrease several hormone-related cancers. Additional studies are ongoing to understand the biological mechanisms associated with weight loss and the increased risk of colorectal cancer. Again, congratulations to all the breast cancer survivors and to all the patients battling all cancers, you remain in our thoughts and prayers!

Be well,

Christopher D. Still, DO, FACN, FACP


  1. Schauer DP, Feigelson HS, Koebnick C, et al. Bariatric surgery and the risk of cancer in a large multisite cohort. Ann Surg. 2019;269(1):95–101.
  2. Bruno DS, Berger NA. Impact of bariatric surgery on cancer risk reduction. Ann Transl Med. 2020;8(Suppl 1):S13.

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