Breast cancer is a complex disease that affects millions of women across the globe each year. Though the American Cancer Society reports that only about 4 percent of women diagnosed with breast cancer in the United States are under age 40, women of all ages can take steps to protect themselves against this deadly disease.

Exercise benefits women in myriad ways, and that includes lowering their risk for breast cancer. The ACS notes that researchers are increasingly linking exercise to a reduced risk for breast cancer. Though the reasons behind that link remain unclear, some theorize that the positive effects of exercise on body weight, inflammation, hormones, and energy balance could be why regular physical activity helps women reduce their risk for breast cancer.

Body weight and breast cancer

The National Cancer Institute reports that being obese after menopause can significantly increase a woman's risk for breast cancer. In addition, the ACS attributes the rise in hormone receptor-positive breast cancers to an increased prevalence of excessive body weight. Routine exercise is a highly effective way to lose weight and keep weight off, which in turn could lower women's risk for breast cancer.

Exercise is a not a sedentary activity, and that could be another reason why women who are physically active have a lower risk for breast cancer. The ACS notes that more than one study has linked sitting time to a higher risk of various diseases, including breast cancer. Researchers with the ACS analyzed data from 77,462 women, who they followed for an average of 15.8 years.

None of the participants had cancer when the study started, but researchers found that women who sat for six or more hours per day during their free time had a 10 percent greater risk for invasive breast cancer than women who sat for less than three hours per day.

Does physical activity reduce breast cancer risk?

The human body is complex, and a host of factors, including those like age that women have no control over, can affect cancer risk. However, engaging in routine physical activity seems to be an effective way for women to reduce their risk for breast cancer. In fact, the Breast Cancer Research Foundation estimates that one-third of all breast cancer cases could be prevented with positive lifestyle choices that help women maintain a healthy weight, including exercise.

Routine physical activity can be a significant weapon in women's arsenal as they continue their efforts to prevent and overcome breast cancer.

Did you know?

Adults who feel good, eat right and exercise regularly may feel as though annual wellness visits are unnecessary, but nothing could be further from the truth.

Data from the Office for National Statistics indicates that, for most cancers, one- and five-year survival rates are significantly higher if the cancer is detected early. But many cancers do not exhibit symptoms in their early stages, or if they do, produce only mild symptoms that do not compel adults to visit their physicians. As a result, annual wellness visits may serve as the only opportunity for physicians to uncover cancers before they reach advanced stages, where survival rates tend to be much lower. During annual physicals, women may receive routine pelvic exams and pap tests, while men may be tested for colon cancer and prostate cancer.

Skipping these visits allows cancers more time to spread, thus complicating treatment plans and potentially reducing survival rates. Annual physicals also may uncover certain factors, such as an unhealthy weight or skin issues like moles, that could be risk factors for cancer or initial warning signs that the disease is present.

Does breast cancer run in families?

No woman is immune to breast cancer. However, some women with family histories of the disease may wonder if they're more vulnerable. According to the Centers for Disease Control and Prevention, roughly 3 percent of breast cancers result from inherited mutations in the BRCA1 and BRCA2 genes that are passed on in families. Inherited mutations in other genes also can cause breast cancer (as well as ovarian cancer), but BRCA1 and BRCA2 are the most commonly affected genes. And it's not just women who can inherit these mutations. Though men account for only a small percentage of breast cancer patients, they can get the disease. The CDC notes that not everyone who inherits a BRCA1, BRCA2 or other mutation will develop breast cancer, and women with such mutations can take steps to help lower their risk. Doctors can discuss those steps with women, but they may include genetic counseling and testing. The CDC also notes that, even in instances when counseling and testing is not ultimately recommended by a physician, women should consider talking to their doctors about starting mammography screening in their 40s. That's earlier than some organizations recommend, though physicians may feel it's worth it