Obesity and Breast Cancer


What is Obesity?
While it is important to have a certain amount of fat in our bodies, too much of a good thing can be bad. When there is too much fat in our bodies it is defined as being overweight or obese. This is actually a serious medical condition which is related to multiple diseases including breast cancer. One way to evaluate this is the BMI (body mass index). BMI is a measure of weight related to height. BMI Values between 25-29.9 are considered overweight, while BMI of 30 or more considered obese, and BMI of 40 or more are extremely obese.

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Obesity and Breast Cancer Risk
Many studies have shown obesity causes an increase in the risk of developing breast cancer in postmenopausal women (women who no longer have menstrual cycles). This seems to be greater in postmenopausal women not taking hormone replacement therapy. The cancer subtype most commonly found in obese patients is ER (estrogen receptor), PR (progesterone receptor) positive breast cancer. This observation is not consistently seen in women who still have menstrual cycles (premenopausal women).

Obesity and Breast Cancer Recurrence & Survival
Obese women have shown a 30% higher risk of recurrence and a 50% higher risk of dying from breast cancer in studies performed by the National Cancer Institute. Additional studies have also shown increased breast cancer recurrence and worse survival in obese patients with breast cancer regardless of their menopausal status.

Possible Mechanisms of Recurrence and Obesity

  • Estrogen building blocks may be converted to estrogen in adipose tissue. Estrogen can make hormone receptor positive breast cancer grow.
  • Obese women have higher levels of insulin than women who are not obese. Insulin can act like a growth factor and cause cancer to grow.

Behavior Modification and Obesity
While many risk factors cannot be changed, weight control is something that is within our power to achieve. A healthy diet, exercise, and weight control may improve survival in breast cancer patients.