> New Year’s Resolution: Get active and lower your breast cancer risk (December 2010)
Being physically active is one of the best things you can do for your health. It helps you maintain a healthy weight and lowers your risk of heart disease, stroke and diabetes. Now, growing scientific evidence shows that it can also help lower your risk of developing or dying from breast cancer.
How might physical activity affect breast cancer?
Physical activity may protect against breast cancer in several ways.
- Body weight. Physical activity helps with weight loss and keeping a healthy weight. Thinner women, as well as those who gain little or no weight during adulthood, have a lower risk of postmenopausal breast cancer [1-4]. On average, thinner breast cancer survivors live longer than heavier survivors. This is because they are less likely to have a recurrence or to die from breast cancer or any other cause (such as heart problems or diabetes) [5-9].
- Estrogen levels in the body. Physical activity may lower estrogen levels in women [10-11], which may, in turn, help prevent breast cancer from developing or spreading [12-13].
- Insulin levels in the body. Physical activity may lower insulin levels in the body . Some data suggest postmenopausal women with lower levels of insulin tend to have a lower risk of developing or dying from breast cancer [14-19].
How is physical activity measured?
To learn whether there is a link between physical activity and breast cancer, studies compare breast cancer rates (or survival) in people who are more active to rates in people who are less active. To do this, researchers must combine the different activities a person does throughout the day into one measure. Researchers often use MET (metabolic equivalent) hours to assess the total amount of activity a person gets. MET hours allow activities that require little energy to be combined with those that require a lot of energy.
The more energy an activity requires, the higher its MET score. For example, one MET hour is the energy used to sit quietly for one hour, but walking for an hour scores from 2.5 to 4.5 MET hours (depending on how quickly you walk). More vigorous activities, like playing tennis, biking or swimming for an hour, score higher. The table below gives examples of the MET hours for some common activities.
Casual walking (less than 2 miles per hour (mph)
Average walking (2 to 2.9 mph)
Brisk walking (3 to 3.9 mph)
Very brisk walking (4 mph or faster)
Jogging, tennis, biking or swimming
Adapted from Wolf et al. 1994 .
Physical activity and breast cancer risk reduction
Regular exercise lowers breast cancer risk by about 20 percent [21-25]. The more active a person is, the greater the benefit appears to be [22,25]. However, you don’t need to have a strenuous exercise routine to benefit. Simply taking a 30-minute walk five times a week instead of sitting still can lower breast cancer risk by about 15 percent in postmenopausal women .
Physical activity and breast cancer survivors
Recurrence and Survival
Studies show that physical activity after a breast cancer diagnosis is associated with a lower risk of recurrence and increased chance of survival [27-29]. Findings from one large study showed that breast cancer survivors who got between nine and 23 MET hours of activity a week (roughly three to nine hours of walking) had a 35 to 40 percent lower risk of recurrence compared to survivors who were less active . The largest study to date on physical activity and survival followed nearly 4,500 breast cancer survivors for more than five years. Survivors who got between three and eight MET hours (roughly one to two hours of brisk walking) of activity a week had a 40 percent lower risk of death compared to less active survivors . Women did not need to do intense exercise to get a survival benefit. Activity equal to a 30-minute brisk walk several times a week improved survival. Women who got more activity got more benefit .
Other benefits for survivors
Physical activity offers other benefits for breast cancer survivors. It can [30-33]:
- Boost positive mood
- Improve physical condition and movement
- Improve body image
- Increase sexuality
- Decrease depression
- Decrease fatigue
Together, these things can help improve the quality of life for breast cancer survivors.
It’s never too late to get active
Breast cancer survivors, including those who were not active before diagnosis, reap many benefits by getting active after treatment ends. Other women can adopt a more active lifestyle at any age and reduce their breast cancer risk.
Some findings show women 50 and older may get more breast cancer risk-lowering benefit from physical activity than younger women . Moreover, a recent study showed women who didn’t exercise much before menopause, but increased their activity to at least nine MET hours a week lowered their breast cancer risk by 10 percent. And, exercising didn’t need to be rigorous. Taking a brisk walk five times a week also lowered risk by about 10 percent . According to Dr. Anne McTiernan, Director of the Prevention Center at the Fred Hutchinson Cancer Research Center, "We are studying how exercise might work in women to prevent breast cancer, or to prevent recurrence in women who have breast cancer. By studying the 'how', we can give women better advice on when, how, how much, and how hard, to exercise, for optimal breast health."
What is Susan G. Komen for the Cure® doing?
As part of our breast self-awareness (BSA) messaging, Komen for the Cure recommends all women add exercise into their routine as part of maintaining a healthy lifestyle which may reduce their risk of breast cancer.
Also, Komen plans to work with the Society for Women’s Health Research (SWHR) to sponsor a Research Network that will support collaboration in the study of exercise and breast cancer. We are very excited about this new partnership. We anticipate this to be a very promising study with useful results.
A final word
Start your New Year’s resolutions a little early and get a jumpstart on the benefits of physical activity. Being active makes you feel good—inside and out. It is one of the few things that you can do to take charge of your health and lower your risk of breast cancer. And, for survivors, regular exercise lowers the chance of recurrence, increases survival and improves quality of life. Adding even a little activity to your day helps improve your health and protects against breast cancer.
So, grab a friend, get active, start improving your health and lower your breast cancer risk today!
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