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How Does Your Body Weight Affect Your Breast Cancer Risk? – Komen Perspectives

Maintaining a healthy weight is one of the best things you can do for your health. However, the percentage of Americans who are overweight or obese is higher than ever.  Currently, about 72 percent of men and 64 percent of women in the U.S. are overweight or obese (defined as a body mass index (BMI) of 25 or higher).1   

What is BMI?
BMI is a ratio of weight (in kilograms) and height (in meters):  


Because BMI includes a measure of height, it gives better comparisons of body weight status among a group of people than weight alone.  For example, two people may weigh the same amount, but one may be tall and lean and the other may be short and stout.  Even though they have the same weight, they would have different BMI and you would be able to compare their body weight status more easily.  For this reason, BMI is the measure most commonly used in research studies on weight and health.   Calculate your BMI

Being overweight or obese is linked to many types of cancer, including postmenopausal breast cancer. Understanding how body weight and weight gain affect your risk of breast cancer both before and after menopause may be a good first step in making healthy lifestyle choices. 

Body weight and breast cancer risk 

Body weight and its effects on breast cancer depend upon whether a woman has gone through menopause.  

  • Before menopause, being overweight modestly decreases the risk of breast cancer.2-5  
  • After menopause, being overweight increases the risk of breast cancer.2-6

Premenopausal breast cancer risk

Before menopause, women who are heavier have a 20 to 38 percent lower risk of developing breast cancer compared to leaner women.3,5,7  This benefit is not well understood and may be limited to estrogen receptor-positive (ER+) breast cancers.8  

Although being overweight seems to offer modest protection against breast cancer in premenopausal women, weight gain should be avoided. Most breast cancers occur after menopause, and any weight you gain before menopause you will likely carry into your postmenopausal years.  

Postmenopausal breast cancer risk

Women who are heavier have a 20 to 60 percent higher risk of postmenopausal breast cancer compared to leaner women.2-6  

Similar to premenopausal weight, body weight after menopause may have the most impact on the risk of ER+ breast cancers. A meta-analysis that combined the results of four studies found postmenopausal women who were heavy had a 70 percent greater risk of ER+ breast cancer compared to those who were lean. However, these heavier women did not have an increased risk of estrogen receptor-negative (ER-) breast cancers.9

Why might body weight affect breast cancer risk?

Although we do not fully understand why breast cancer risk differs in pre- and postmenopausal women, the hormone estrogen likely plays a role. Women with higher estrogen levels have an increased risk of breast cancer (learn more).10  

In premenopausal women, most of the estrogen in the body is produced in the ovaries. Weight has little effect on this estrogen. In postmenopausal women, the main source of estrogen is fat which contains an enzyme that makes estrogens. So, heavier postmenopausal women tend to have higher estrogen levels compared to leaner postmenopausal women. This extra estrogen likely explains the increased breast cancer risk among postmenopausal women who are overweight.11

Women who are heavier also tend to have higher levels of insulin in their bodies compared to leaner women.12 Some studies have shown an increased risk of breast cancer among postmenopausal women with high levels of insulin including women with type 2 diabetes.13-16 Among premenopausal women, findings on a possible link between insulin levels and breast cancer risk are less clear.17-18 These topics are still under study. 

Weight gain during adulthood and breast cancer risk

Postmenopausal breast cancer

Weight gain after age 18 appears to increase the risk of breast cancer in postmenopausal women. Study findings show the more weight women gain, the more their breast cancer risk tends to increase.6,19-21 For example, findings from the Nurses Health Study showed  women who gained about 10 to 45 pounds after age 18 had a 15 percent greater breast cancer risk compared to women with little weight change. Women who gained more than 55 pounds after age 18 had a 45 percent increase in postmenopausal breast cancer risk.21

It’s not just the weight gained from age 18 that seems to be important to risk. Even among women who gain weight after menopause, there appears to be an increased risk of breast cancer. The National Institutes of Health-American Association of Retired Persons Health Study found women who gained more than 66 pounds after age 50 had an 89 percent increased risk of breast cancer.6

Premenopausal breast cancer

To date, only a few studies have addressed weight gain and premenopausal breast cancer risk. Most have shown no link between the two, but this topic is still under study.22-24 

Weight loss and breast cancer risk

The good news is that for women who are overweight, losing weight may help lower breast cancer risk. And, it’s never too late to start. One large study found women who lost four to 11 pounds after menopause had more than a 20 percent lower risk of breast cancer compared to women whose weight did not change.21 

According to Dr. Jennifer Ligibel, assistant professor of medicine at Harvard Medical School, “Many women ask how they can lower their risk of breast cancer.  One of the important things about identifying excess weight as a risk factor for breast cancer is that, unlike many of the other risk factors for breast cancer that women can’t do anything about (like being a woman or getting older), weight is something that a woman can modify to potentially lower her risk of developing breast cancer.  Although losing weight isn’t easy, it might help a woman avoid breast cancer.  We also know that keeping your weight in a healthy range helps to lower the risk of many other health problems such as heart disease and diabetes.  A healthy diet and moderate exercise should be part of a healthy lifestyle for all women.” 

Future directions in research

During adolescence, girls enter puberty and their breasts begin to mature. Because this is an important time of breast growth and development, body weight during adolescence may play an early role in breast cancer risk. Some study findings suggest girls who are heavier than average during adolescence have a decreased risk of pre- and postmenopausal breast cancer.23,25-26 And, some findings suggest girls who are leaner than average also have a decreased risk of breast cancer.25 These relationships are under active study and reflect the complex links between body weight throughout life and breast cancer risk. 

The benefits of maintaining a healthy weight

Avoiding weight gain not only helps protect against breast cancer, it also has many other health benefits. Compared to women who are overweight or obese, women with a healthy weight have a lower risk of pancreatic, endometrial, ovarian, kidney and other types of cancer.5,27-30 And, they are less likely to develop other health problems, including:31-32

  • Heart disease 
  • Stroke 
  • Type 2 diabetes 
  • High blood pressure 
  • Liver and gallbladder disease 
  • Sleep apnea and other breathing problems 

Healthy lifestyle choices-it’s never too late to change

With so many risk factors for breast cancer out of our hands (like age, being female and genetic factors), body weight is one of the few things most of us can try to control. And, making healthy lifestyle choices has benefits at any age. Getting regular physical activity and eating a balanced diet are the best ways to avoid weight gain and maintain a healthy weight at any point in life.  

In our busy lives, making healthy choices can be easier said than done. Fortunately, there are many resources available to help you plan a healthy diet and make simple changes to your daily life to increase activity. Your health care provider is a good place to start.  And, many websites offer tips on adopting a healthier lifestyle, including:  

Centers for Disease Control and Prevention (CDC)

Find tips on healthy ways to prevent weight gain or lose weight.

Department of Agriculture’s
Create a personalized daily food plan (designed to maintain or lose weight) and find tips on balancing calories and making healthy food choices.

National Heart, Lung, and Blood Institute (NHLBI)

Find a menu planner, tips on being physically active and other tools for maintaining a healthy weight.


1. Flegal KM, Carroll MD, Ogden CL, Curtin LR. Prevalence and trends in obesity among US adults, 1999-2008. JAMA. 303(3):235-41, 2010. 

2. Tretli S. Height and weight in relation to breast cancer morbidity and mortality. A prospective study of 570,000 women in Norway. Int J Cancer. 44:23-30, 1989.  

3. Huang Z, Hankinson SE, Colditz GA, et al. Dual effects of weight and weight gain on breast cancer risk. JAMA. 278(17):1407-1411, 1997.  

4. van den Brandt PA, Speigelman D, Yaun S, et al. Pooled Analysis of Prospective Cohort on Height, Weight, and Breast Cancer Risk. Am J Epidemiol. 152(6):514-527, 2000. 

5. Reeves GK, Pirie K, Beral V, Green J, Spencer E, Bull D. Cancer incidence and mortality in relation to body mass index in the Million Women Study: cohort study. BMJ. 335(7630):1134, 2007.  

6. Ahn J, Schatzkin A, Lacey JV Jr, et al. Adiposity, adult weight change, and postmenopausal breast cancer risk. Arch Intern Med. 167(19):2091-102, 2007.  

7. Michels K, Terry KL, Willett WC. Longitudinal study on the role of body size in premenopausal breast cancer. Arch Intern Med. 166(21):2395-402, 2006.  

8. Yang XR, Chang-Claude J, Goode EL, et al. Associations of breast cancer risk factors with tumor subtypes: a pooled analysis from the Breast Cancer Association Consortium studies. J Natl Cancer Inst. 103(3):250-63, 2011. 

9. Suzuki R, Orsini N, Saji S, Key TJ, Wolk A. Body weight and incidence of breast cancer defined by estrogen and progesterone receptor status–a meta-analysis. Int J Cancer. 124(3):698-712, 2009.  

10. The Endogenous Hormones and Breast Cancer Collaborative Group. Endogenous sex hormones and breast cancer in postmenopausal women: reanalysis of nine prospective studies. J Natl Cancer Inst. 94(8): 606-616, 2002. 

11. Key TJ, Appleby PN, Reeves GK, et al. for the Endogenous Hormones Breast Cancer Collaborative Group. Body mass index, serum sex hormones, and breast cancer risk in postmenopausal women. J Natl Cancer Inst. 95(16):1218-26, 2003. 

12. Pichard C, Plu-Bureau G, Neves-E Castro M, Gompel A. Insulin resistance, obesity and breast cancer risk. Maturitas. 60(1):19-30, 2008. 

13. Michels KB, Solomon CG, Hu FB, et al. for the Nurses’ Health Study. Type 2 diabetes and subsequent incidence of breast cancer in the Nurses’ Health Study. Diabetes Care. 26(6):1752-8, 2003.  

14. Lipscombe LL, Goodwin PJ, Zinman B, McLaughlin JR, Hux JE. Diabetes mellitus and breast cancer: a retrospective population-based cohort study. Breast Cancer Res Treat. 98(3):349-56, 2006.  

15. Larsson SC, Mantzoros CS, Wolk A. Diabetes mellitus and risk of breast cancer: a meta-analysis. Int J Cancer. 121(4):856-62, 2007.  

16. Barone BB, Yeh HC, Snyder CF, et al. Long-term all-cause mortality in cancer patients with preexisting diabetes mellitus: a systematic review and meta-analysis. JAMA. 300(23):2754-64, 2008. 

17. Del Giudice ME, Fantus IG, Ezzat S, et al. Insulin and related factors in premenopausal breast cancer risk. Breast Cancer Res Treat. 47:111-20, 1998.  

18. Eliassen AH, Tworoger SS, Mantzoros CS, Pollak MN, Hankinson SE. Circulating insulin and c-peptide levels and risk of breast cancer among predominately premenopausal women. Cancer Epidemiol Biomarkers Prev. 16(1):161-4, 2007. 

19. Feigelson HS, Jonas CR, Teras LR, Thun MJ, Calle EE. Weight gain, body mass index, hormone replacement therapy, and postmenopausal breast cancer in a large prospective study. Cancer Epidemiol Biomarkers Prev. 13(2):220-4, 2004.  

20. Sweeney C, Blair CK, Anderson KE, et al. Risk factors of breast cancer in elderly women. Am J Epidemiol. 160(9):868-75, 2004.  

21. Eliassen AH, Colditz GA, Rosner B, et al. Adult weight change and risk of postmenopausal breast cancer. JAMA. 296(2):193-201, 2006.  

22. Lahmann PH, Schulz M, Hoffmann K, et al. Long-term weight change and breast cancer risk: the European prospective investigation into cancer and nutrition (EPIC). Br J Cancer. 93(5):582-9, 2005.  

23. Palmer JR, Adams-Campbell LL, Boggs DA, Wise LA, Rosenberg L. A prospective study of body size and breast cancer in black women. Cancer Epidemiol Biomarkers Prev. 16(9):1795-802, 2007. 

24. Michels KB, Terry KL, Eliassen AH, Hankinson SE, Willett WC. Adult weight change and incidence of premenopausal breast cancer. Int J Cancer. 2011 Mar 16 [Epub ahead of print]. 

25. Coates RJ, Uhler RJ, Hall HI, et al. Risk of breast cancer in young women in relation to body size and weight gain in adolescence and early adulthood. Br J Cancer. 81(1):167-74, 1999. 

26. Bardia A, Vachon CM, Olson JE, et al Relative weight at age 12 and risk of postmenopausal breast cancer. Cancer Epidemiol Biomarkers Prev. 17(2):374-8, 2008.  

27. Michaud DS, Giovannucci E, Willett WC, Colditz GA, Stampfer MJ, Fuchs CS. Physical activity, obesity, height, and the risk of pancreatic cancer. JAMA. 286(8):921-9, 2001. 

28. Leitzmann MF, Koebnick C, Danforth KN, et al. Body mass index and risk of ovarian cancer. Cancer. 115(4):812-22, 2009. 

29. Thomas CC, Wingo PA, Dolan MS, Lee NC, Richardson LC. Endometrial cancer risk among younger, overweight women. Obstet Gynecol. 114(1):22-7, 2009. 

30. Arslan AA, Helzlsouer KJ, Kooperberg C, et al. for the Pancreatic Cancer Cohort Consortium (PanScan). Anthropometric measures, body mass index, and pancreatic cancer: a pooled analysis from the Pancreatic Cancer Cohort Consortium (PanScan). Arch Intern Med. 170(9):791-802, 2010. 

31. Centers for Disease Control and Prevention (CDC). Overweight and obestity., 2011. 

32. National Heart, Blood and Lung Institute (NHLBI). Overweight and obesity. U.S. Department of Health and Human Services, NHLBI., 2010.