Linking Obesity to Breast Cancer

Breast cancer is the second most common cancer in women worldwide, representing 16% of all cancers in women. Although early diagnosis and available treatments have improved survival rates, new prevention strategies are sought to reduce the incidence of this disease.

A new study published in the Journal of Cell Physiology describes how inflammation that characterizes fatty tissue is one of the main microenvironment actors responsible for promoting cancer. The authors also describe the involvement of steroid hormones and others factors produced by adipose tissue in breast cancer development. The study, “Multifaceted breast cancer: the molecular connection with obesity,” appeared in the July 1, 2016 edition of the international, per-reviewed journal focused on cancer-related issues.

Increasingly, obesity has been identified as a significant risk factor for many cancers and, after tobacco use, may be the single greatest modifiable cancer risk factor. Excess body weight may affect cancer risk through a number of mechanisms, some of which might be specific to certain cancer types. Excess body fat might affect:

  • Immune system function and inflammation
  • Levels of certain hormones, such as insulin and estrogen
  • Factors that regulate cell growth, such as insulin-like growth factor-1 (IGF-1)
  • Proteins that influence how the body uses certain hormones, such as sex hormone-binding globulin

Many studies have shown that being overweight and obese are associated with a modest increase in risk of postmenopausal breast cancer. This higher risk is seen mainly in women who have never used menopausal hormone therapy (MHT) and for tumors that express both estrogen and progesterone receptors. In contrast, being overweight and obese been found to be associated with a reduced risk of premenopausal breast cancer in some studies.

The relationship between obesity and breast cancer may be affected by the stage of life in which a woman gains weight and becomes obese. Epidemiologists are actively working to address this question. Weight gain during adult life, most often from about age 18 to between the ages of 50 and 60, has been consistently associated with risk of breast cancer after menopause.

The increased risk of postmenopausal breast cancer is thought to be due to increased levels of estrogen in obese women. After menopause, when the ovaries stop producing hormones, fat tissue becomes the most important source of estrogen. Because obese women have more fat tissue, their estrogen levels are higher, potentially leading to more rapid growth of estrogen-responsive breast tumors.

The relationship between obesity and breast cancer risk may also vary by race and ethnicity. There is limited evidence that the risk associated with overweight and obesity may be less among African American and Hispanic women than among white women.

While we still have much to learn about the link between weight loss and cancer risk, people who are overweight or obese should be encouraged and supported if they try to lose weight. Aside from possibly reducing cancer risk, losing weight can have many other health benefits, such as lowering the risk of heart disease and diabetes.

Bottom line: Obesity is associated with an increased risk of breast cancer and other cancers as well. Being overweight or obese also leads to a greater risk for many diseases, including diabetes, high blood pressure, cardiovascular diseases, and stroke. The best response is prevention with a proactive lifestyle focused on a healthy diet and regular exercise.

About the author: Raja P. Reddy, MD is a board certified diagnostic radiologist specializing in breast imaging. He is also a contributing editor for Digital Mammography Specialists, a leading provider of outpatient women’s imaging services in the greater Atlanta, GA.