Body fat and its role in breast cancer
General obesity more strongly associated with postmenopausal breast cancer risk than abdominal obesity
Among factors that influence breast cancer risk, body fat has been shown to play a role, but studies on fat distribution are uncertain. A new large-scale study conducted in Europe and published May 17, 2004 in the online edition of the International Journal of Cancer – the official journal of the International Union Against Cancer (UICC) – found that in postmenopausal women, general obesity, not abdominal fat, is associated with increased breast cancer risk. The full study is available online via Wiley InterScience at http://www.interscience.wiley.com/journal/ijc.
Previous studies that have examined the relationship between body size and incidence of breast cancer suggest that taller women are at increased risk regardless of whether they have reached menopause, and that obesity is associated with a reduced risk of breast cancer in premenopausal women and an increased risk in postmenopausal women, although results of studies on abdominal fat are equivocal. Hormone replacement therapy (HRT) has also been shown to significantly increase the risk of breast cancer in earlier studies.
In order to estimate the relative risk of breast cancer in relation to general and abdominal obesity and evaluate whether HRT plays a role in this relationship, a study was conducted by Petra H. Lahmann, Ph.D. of the German Institute of Human Nutrition in Potsdam-Rehbrücke, Germany. The study was based on the European Prospective Investigation into Cancer and Nutrition (EPIC), a large prospective cohort study coordinated by Dr. Elio Riboli at the International Agency for Research on Cancer (IARC-WHO), Lyon, France. Researchers examined measurements of height, weight, body mass index (BMI), and waist and hip circumference from 73,542 premenopausal and 103,344 postmenopausal women from nine European countries. During 4.7 years of follow-up, 1,879 invasive breast cancers were identified.
Results showed that body size was more strongly associated with breast cancer risk in postmenopausal women than premenopausal women. Height was linked to breast cancer risk in both groups, but more significantly in postmenopausal women. The reasons for this are not well understood, but may be explained by factors that influence both bone growth and breast cancer, such as birth weight, diet, infection, energy balance and insulin-like growth factors. In postmenopausal women, obesity was linked to increase risk of breast cancer in women who were not using HRT, while those on HRT with a low BMI had an increased risk. In terms of fat distribution, hip circumference was a strong predictor of postmenopausal breast cancer in women not using HRT, but waist circumference, controlled for overall body fat (BMI), was not significantly related to increased breast cancer risk, neither in post- nor in premenopausal women.
The authors conclude: "Overweight is one of the few modifiable breast cancer risk factors and thus an important measure for breast cancer prevention and prognosis."
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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