But as interesting and useful as this study may be, it has a number of practical limitations:
Despite these limitations, there are some important take-home messages from this study and from other recent studies:
Check out our Ask-the-Expert Online Conference from January 2005 for practical advice on how to lose weight.
Other important things you can do to increase breast health and lower your risk of breast cancer include:
Visit breastcancer.org's Lower Your Risk section to find out about other protective measures you can take.
Finally, for women who have a strong family history of breast cancer or who have a proven breast cancer gene abnormality, genetic counseling and testing can help guide your care. Education and counseling are the first steps in assessing your genetic risk. There are a lot of pros and cons to genetic testing. Talk to your doctor or a genetic counselor to assess the value of genetic testing in your situation and the other steps you can take to lower your risk and improve your breast health.
Reviewed study: "Weight Loss in 20s Reduces Risk in Women With Abnormal BRCA Genes" by J. Kotsopoulos et al., Breast Cancer Research, August 19, 2005
Is this for me? If you are a young woman with a strong family history of breast cancer or a known breast cancer gene abnormality (like an abnormal BRCA1 or BRCA2 gene), you might want to read this article.
Background and importance of the study: Abnormal BRCA1 and BRCA2 (BR stands for BReast, and CA stands for CAncer) genes account for about 5–10% of all breast cancers. The average woman (without an inherited abnormal breast cancer gene) in the United States has about a 12% risk of developing breast cancer over a 90-year life span. Women who have an abnormal BRCA1 or BRCA2 gene have up to an 85% risk of developing breast cancer by age 70.
Research has shown that overweight women have a higher risk of getting breast cancer after menopause. This is most likely because the extra fat cells make various hormones, including extra estrogen. Other research has found that being overweight can increase the risk of breast cancer coming back (recurrence).
In this study, researchers looked to see if gaining or losing weight affects the risk of breast cancer in women with an abnormal BRCA1 or BRCA2 gene.
Study design: To see how changes in body weight affect the risk of breast cancer in women with an abnormal BRCA1 or BRCA2 gene, the researchers conducted what's known as a matched case-control study. This means that they studied pairs of women, both of whom had an abnormal BRCA1 or BRCA2 gene—one woman diagnosed with breast cancer (the case) and one woman who had not been diagnosed (the control).
The women in the study were participants in earlier and ongoing clinical research trials.
The researchers looked at 1,073 case-control pairs of women (2,146 women total) from five countries: United States, Canada, United Kingdom, Poland, and Israel.
All of the women in the study completed a questionnaire while being interviewed by the researchers. The questionnaire asked about the women's:
The researchers then used statistical analysis to study the association between weight gain or loss and the risk of breast cancer.
The study was conducted from 1988 to 2004 by researchers from the United States, Canada, and Poland.
Results: When the researchers looked at all women in the study, they found that losing at least 10 pounds between the ages of 18 and 30 was associated with a 34% decrease in the women's risk of developing breast cancer. This reduction in risk was statistically significant, meaning that it was because of the weight loss and not just due to chance.
The researchers also found that this weight loss was associated with a 53% reduction in the risk of breast cancer diagnosed between the ages of 30 and 40. This reduction in risk was also statistically significant. This is important to know because abnormal BRCA1 and BRCA2 genes often cause breast cancer to develop in women before age 40. It should be noted, however, that the weight loss did not affect the risk of breast cancer after age 40.
Gaining weight between the ages of 18 and 30 was not associated with an increase in the overall risk of breast cancer.
The researchers also looked at the results by the type of abnormal gene (BRCA1 or BRCA2). In women with an abnormal BRCA1 gene, a weight loss of at least 10 pounds between the ages of 18 and 30 was associated with a 65% reduction in breast cancer risk. This result is statistically significant. In women with an abnormal BRCA2 gene, a weight loss of 10 pounds between the ages of 18 and 30 was associated with a 12% reduction in breast cancer risk, but this result was not statistically significant.
Also, in women with an abnormal BRCA1 gene who had at least two children, a weight gain of 10 or more pounds between ages 18 and 30 was associated with a 44% increase in the risk of developing breast cancer between the ages of 30 and 40. This result was statistically significant.
Conclusions: The researchers concluded that women with an abnormal BRCA1 or BRCA2 gene who lose weight in early adulthood (between ages 18 and 30) decrease their risk of developing BRCA-associated breast cancer at a young age. They also concluded that women who have an abnormal BRCA1 gene should try to avoid gaining weight in their 20s, especially if they choose to have children.
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