Post-Menopausal Breast Cancer
Obesity and the Risk of Post-menopausal Breast Cancer
It is becoming increasingly apparent in recent scientific and medical research that obesity and many forms of cancer are directly related. The risks of developing breast cancer in postmenopausal women have also been studied and noted at length. (1)(2)(3)(4) The Cornell University’s Fact Sheet #56 has extensive information about the relationship between the risks of developing breast cancer and obesity. (5) Generally, it is understood that obesity has a direct relationship to the risks of developing breast cancer. Women who have a high body mass index (BMI) after they have gone through menopause generally have a high chance of developing breast cancer. To clarify further, the studies state that obesity before menopause slightly weakens your chances of developing breast cancer, while obesity after menopause moderately to significantly increases your chances of developing breast cancer. But because obesity is generally linked to many other types of cancer (endometrial, ovarian, colonorectal), it is generally not advised that obesity be used as a preventative for breast cancer. In fact, for the healthiest possible lifestyle it is advisable to maintain a BMI of between 18 and 24 by eating well-balanced, healthy meals and regular, frequent exercise. The sedentary lifestyles of modern, Western developed nations indirectly promote obesity and being overweight. Entertainment choices such as excessive television watching, surfing the Internet are all related to obesity. In addition, many people sit for hours on end in front of computers at the office and reducing your inactivity by introducing regular breaks where you stand up and walk around the office, or go outside and take a walk while eating your sandwich or taking a 15 minute break are all things that everyday people can introduce to their lifestyles to remain healthier.
Obesity is simply defined as having too much body fat. (6) This is not the same as body weight. Visceral body fat, in other words, body fat that is excessive to the needs of a healthy, functioning human body (which usually layers around the abdominal area), can have a negative influence on your body. Body fat in most recent and modern scientific definitions has been recognized as a necessary organ in the body. Body fat releases a hormone into the body known as leptin, which plays a major role in regulating metabolism, body-weight and energy expenditure. (7) When an excess of body-fat builds up in the human body, then what happens is that the body becomes overdosed and desensitized to the appetite-suppressing effects of leptin. (8) The side effect of this is that the body then craves more and more food and it becomes a vicious cycle of gaining weight and food consumption.
There are several aspects of obesity which are important to determine the risks of the development of breast cancer. For instance, the greater the body-weight of an individual before menopause actually reduces the risk of cancer, while greater body-weight after menopause will increase the risk. (9) This is undoubtedly related to the fact that it is normal, if not even healthy, for women to gain weight in their child-rearing years, particularly during pregnancy. This is not, however, to be taken as a license to become overweight in order to protect against breast cancer, as so many other cancers are directly related to obesity as well (endometrial, colonorectal, ovarian). The data analyzed for this important information was collected from a pool of 337,819 women of which 4,385 developed breast cancer. The data collated information from seven separate studies. (10) The findings were that postmenopausal women weighing more than 176 pounds had “a weak increase in breast cancer risk compared to women weighing less than 132 pounds.” (11) Additionally, women who were before their menopause and weighed more than 176 pounds had a moderate risk of developing breast cancer compared to women who weighed less than 132 pounds
The relationship to body mass index
Body mass index is generally taken to be a better measure of obesity than pure weight alone, because it takes into account other factors such as age, body type and body height and gives an overall more balanced picture of someone’s health. The relationship is actually quite similar to the one that body weight has to breast cancer - in that a woman who has a BMI greater than 33 before menopause compared to a woman who has a BMI less than 21 has a lower risk of developing breast cancer, while a postmenopausal woman with a BMI greater than 33 had a higher risk in developing breast cancer compared to lighter women. (12) Also mentioned in the studies collated on Cornell University’s Fact Sheet is the information that there seems to be no relationship between breast cancer and obesity in women who have undergone hormone therapy, but the epidemiologic studies have shown that this is due to the masking of the effect of obesity by hormone threapy.
The link to weight gain and weight loss
Because an adult body is already at full development, most weigh-gain is due to the accumulation of fat tissue. Due to this, many studies have examined the link between weight-gain and the risks of breast cancer. While most studies have focused on the effects of weight-gain on adults who develop breast cancer, an increasing number of them are now investigating how the effect could be different for undeveloped women. In fact, what the studies have shown is that sudden gains in weight increase the risk of developing breast cancer, while exactly the opposite seems to be true for weight loss: losing weight can lower your risk of developing breast cancer.
How fat cells interact with the risks of breast cancer
Fat cells release substances such as leptin, adiponectin, resistin and tumor necrosis factor-alpha. (14) All of these have effects on breast cells in the laboratory and can increase breast cancer risk as they are hormones. Obesity also leads to a larger exposure to estrogen as well as other hormonal changes that can potentially increase the risk of developing breast cancer.
The message is clear: maintaining your BMI at appropriate levels throughout your lifetime is the best way to combat the risks of developing breast cancer.
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(1) Obesity, body size, and risk of postmenopausal breast cancer: the Women's Health Initiative (United States), Morimoto LM, White E, Chen Z, Chlebowski RT, Hays J, Kuller L, Lopez AM, Manson J, Margolis KL, Muti PC, Stefanick ML, McTiernan A., Cancer Causes Control. 2002 Oct;13(8):741-51. Retrieved 30th June, 2011, http://www.ncbi.nlm.nih.gov/pubmed/12420953
(2) Obesity and outcomes in premenopausal and postmenopausal breast cancer.
Loi S, Milne RL, Friedlander ML, McCredie MR, Giles GG, Hopper JL, Phillips KA., Loi S, Milne RL, Friedlander ML, McCredie MR, Giles GG, Hopper JL, Phillips KA., Cancer Epidemiol Biomarkers Prev. 2005 Jul;14(7):1686-91. Retrieved 30th June, 2011, http://www.ncbi.nlm.nih.gov/pubmed/16030102
(3) OBESITY AND POSTMENOPAUSAL BREAST CANCER RISK:
A LITERATURE REVIEW, Diala Ata Al-Dajani, Middle East Journal of Nursing, January 2011- Volume 5, Issue 1. Retrieved 30th June, 2011, http://www.me-jn.com/Vol5%20Issue1/obesity.htm
(4) Body Composition and Breast Cancer in Postmenopausal Women: A Danish Prospective Cohort Study, Lene Mellemkjær*, Janne Bigaard*, Anne Tjønneland, Jane Christensen, Birthe Thomsen, Christoffer Johansen, Kim Overvad and Jørgen H. Olsen, Obesity (2006) 14, 1854–1862; doi: 10.1038/oby.2006.214. Retrieved 30th June, 2011, http://www.nature.com/oby/journal/v14/n10/full/oby2006214a.html
(5) Obesity and Breast Cancer Risk, Fact Sheet #56, Barbour Warren, Carol M Devine, Program on Breast Cancer and Environmental Risk Factors in New York State. Retrieved 30th June, 2011, http://envirocancer.cornell.edu/FactSheet/diet/fs56.obesityBCRisk.cfm
(6) ibid.
(7) Obesity and colon cancer link, David Bradley, Sciencebase. Retrieved 24th June, 2011, http://www.sciencebase.com/science-blog/obesity-and-colon-cancer-link.html
(8) http://en.wikipedia.org/wiki/Leptin. Retrieved 24th June, 2011.
(9) Obesity and Breast Cancer Risk, Fact Sheet #56, Barbour Warren, Carol M Devine, Program on Breast Cancer and Environmental Risk Factors in New York State. Retrieved 30th June, 2011, http://envirocancer.cornell.edu/FactSheet/diet/fs56.obesityBCRisk.cfm
(10) ibid.
(11) ibid.
(12) ibid.
(13) ibid.
(14) ibid.