Gaining Weight after Menopause Seems to Increase Breast Cancer Risk in Post-Menopausal Women
Reviewed study: "Gaining Weight After Menopause Seems to Increase Breast Cancer Risk in Post-Menopausal Women" by A. Heather Eliassen and others, Journal of the American Medical Association, July 12, 2006
Is this for me? If you're trying to lower your breast cancer risk during menopause and after, you might want to read this article.
What question is this study trying to answer? The researchers wanted to analyze the relationship between a woman's gaining or losing weight as an adult (after age 18 as well as after menopause) and her breast cancer risk when she is post-menopausal.
Overweight women have an increased risk, compared to average-weight women, of getting breast cancer after menopause. And being overweight can increase the risk of breast cancer coming back in women who have had the disease. This may be because fat cells make extra estrogen and other hormones, which might stimulate breast cell growth.
Many studies have shown a connection between weight gain and increased breast cancer risk. But so far, only a few studies have looked at how gaining or losing weight after menopause affects breast cancer risk, and these studies have been too small to give solid results.
Study design: The researchers analyzed information from a group of post-menopausal women who are participating in the Nurses' Health Study. The Nurses' Health Study is a study of 121,700 women who were married, registered nurses, and 30 to 55 years old when the study started in 1976. Every two years, the women fill out mailed questionnaires on lifestyle factors, including many factors that affect breast cancer risk, such as weight.
From the larger Nurses' Health Study, the researchers analyzed the weight gain or weight loss of post-menopausal women during two age periods in their lives:
- since age 18 (87,143 women)
- since menopause (49,514 women)
The researchers looked at the relationship between the number of cases of breast cancer diagnosed in both groups and changes in body weight.
Women who had a history of cancer were excluded from the study. The researchers also took into account other factors that can influence breast cancer risk:
- age at first period
- age at first completed pregnancy
- age at menopause
- number of children
- body mass index
- weight at age 18
- alcohol use
- family history of breast cancer
While the women had to remember their weight at age 18, this information was checked against college and nursing school records and was found to be accurate within about 3 pounds.
The women were followed for up to 24 years.
This study was funded by the National Cancer Institute, the Department of Defense and Cancer Education, and the American Cancer Society.
Study results:
Analysis of weight gain after menopause: Women who weighed within 4.4 pounds of their weight at age 18 were considered to have maintained their weight. Compared to those women, women who gained 22 pounds or more after menopause had an 18% increase in their relative risk of breast cancer.
There were 2,376 cases of breast cancer diagnosed in women whose weight had increased since menopause. There were 621 cases of breast cancer diagnosed in women who maintained their weight since menopause.
Women who LOST at least 22 pounds after menopause had a 23% reduction in their relative risk of breast cancer.
Analysis of weight gain after age 18: Compared to women who maintained their weight, women who gained 55 pounds or more since age 18 had a 45% increase in their relative risk of breast cancer. There were 4,393 cases of breast cancer diagnosed in women whose weight change since age 18 had been documented.
Women who lost at least 22 pounds after age 18 but before menopause had a 16% reduction in their relative risk of breast cancer, compared to women who maintained their weight. Women who maintained this weight loss after menopause had a 57% reduction in their relative risk of breast cancer, compared to women who maintained their weight.
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What breastcancer.org says about this article…
Gaining Weight after Menopause Seems to Increase Breast Cancer Risk in Post-Menopausal Women
This large, long study is a major addition to the growing body of work showing that weight gain can increase breast cancer risk. It offers more evidence that extra weight throughout your adult life (after 18) can increase breast cancer risk. This also was true for women who gained weight after menopause. Plus, the bigger the weight gain, the higher the risk. The good news is that weight loss was associated with a decreased risk of breast cancer.
There are probably several reasons that gaining weight is associated with an increased risk of breast cancer. Extra fat cells make extra estrogen and other hormones that might stimulate breast cell growth. Plus, women who weigh more tend to exercise less and eat higher-fat foods.
Weight gain is a VERY sensitive topic. This is especially true for women who have had breast cancer, since weight gain is a common and very upsetting side effect of treatment. Plus, as we age, it's harder to keep weight under control because our metabolism slows down and we tend to get less exercise.
You might be thinking: How can the treatment I took to REDUCE my risk of breast cancer cause a side effect that could INCREASE my risk? But the important benefits of breast cancer treatment are much greater than the increase in risk. It's true that getting rid of the extra pounds will take work, whether they were already there when breast cancer was diagnosed or whether they jumped on during treatment.
The bottom line is that NOW is the time to get rid of the extra pounds. Losing weight can help reduce your risk of breast cancer, on top of medical treatment and other lifestyle changes. Right after treatment, and during hormonal therapy, losing weight is particularly challenging. But even at this point, you can start to make real progress. It's no secret: a healthy low-fat, low-calorie, balanced diet and regular physical activity are the basic components of losing weight. Our Ask-the-Expert Online Conference from January 2005 has some good general tips on losing weight.
Because it's often hard to lose weight by yourself, breastcancer.org also has a discussion board called The Pound. The Pound helped our president and founder Dr. Marisa Weiss, get on track. She lost 20 pounds and is working hard to keep it off.