Home

About Breast Health


Avoiding Obesity and Weight Gain

Avoiding Obesity

Women should pursue a health strategy that will reduce the known breast cancer risk factors as much as possible, including avoiding obesity and weight gain, increasing physical activity and managing lifestyle choices. IARC estimates that excess body weight and physical inactivity account for approximately 25–33% of breast cancer cases1.

Recent studies indicate that women who avoid being overweight reduce their risk of postmenopausal breast cancer. This risk is independent of the effect of physical activity. It is important for women to limit their weight gain in adult life and maintain a body mass index (BMI) of 18.5-24.9. Postmenopausal overweight /obesity is associated with an increased risk of breast cancer. There is an inverse relationship between obesity (BMI of 30 or higher) and breast cancer in pre-menopausal women and a direct relationship in post-menopausal women.

  • A large amount of abdominal fat may increase the risk of breast cancer
  • Obese women tend to have more abnormal mammography readings than non-obese women

Body Mass Index (BMI)

Being overweight with a BMI of 25 or higher, or obese with a BMI of 30 or greater, points to an increased risk of developing postmenopausal breast cancer2. Women who have already had breast cancer may help reduce their risk of further problems by keeping their weight within the normal range.


More Research on Avoiding Obesity and Weight Gain

“Cancer incidence and mortality in relation to body mass index in the Million Women Study: cohort study”
Reeves GK, Pirie K, Beral V, Green J, Spencer E, Bull D
BMJ 2007;335:1134

Increasing body mass index (BMI) was associated with a significant increase in the risk of several cancer types, among them breast cancer in postmenopausal women. Read More…


“Overweight, Obesity, and Postmenopausal Invasive Breast Cancer Risk
A Secondary Analysis of the Women’s Health Initiative Randomized Clinical Trials”
Neuhouser ML, Aragaki AK, Prentice RL, et al.
JAMA Oncol. 2015;1(5):611-621

Obesity is associated with increased invasive breast cancer risk in postmenopausal women. These clinically meaningful findings should motivate programs for obesity prevention. Read More…


“Body Fat Distribution and Risk of Premenopausal Breast Cancer in the Nurses’ Health Study II”
Harris HR, Willett WC, Terry KL, Michels KB
J Natl Cancer Inst. (2011) 103 (3): 273-278

Findings suggest that body fat distribution is associated with an increased risk for ER-negative breast cancer.
Read More…


1: IARC (2002). IARC Handbooks of Cancer Prevention, Volume 6, Weight control and physical activity. Lyon, France: International Agency for Research on Cancer.
2: Stewart BW, Wild CP, editors (2014). World Cancer Report 2014. Lyon, France: International Agency for Research on Cancer