From the link I posted
ACKNOWLEDGMENT
The editorial staff at UpToDate, Inc. would like to acknowledge Dr. Mary Costanza, who contributed to an earlier version of this topic review
Literature review current through: Apr 2014. | This topic last updated: Jan 15, 2013.
STANDARD RISK FACTORS
Increasing age — The primary risk factor for breast cancer in most women is older age. The incidence of breast cancer rises sharply with age until the age of 45 to 50, at which point the rise is less steep. At age 75 to 80, the incidence rates flatten out and then start to decline after this.
Gender — Breast cancer is the most common cancer in women and occurs 100 times more commonly in women than in men.
Race/ethnicity — In the United States, white women have the highest rate of breast cancer; for every 100,000 women, there are 124 cases diagnosed. The rate of breast cancer is lower in black women (113 per 100,000), American Indians/Alaska natives (92 per 100,000), and Hispanic women (90 per 100,000). It is lowest in Asian Americans/Pacific Islanders (82 per 100,000).
Weight — The impact of both weight gain and obesity is mostly associated with an increased risk of postmenopausal breast cancer. A higher body mass index (BMI) is associated with a lower risk of premenopausal breast cancer, although the mechanism behind this association is not clear.
Tall stature — Tall stature is associated with an increased risk of breast cancer. In studies, women who were at least 69 inches were more likely to develop breast cancer compared to women less than 63 inches tall.
Increased estrogen exposure
Benign breast disease — In addition to breast cancer, women can develop abnormal breast findings. These breast abnormalities can develop because of excessive growth of the glandular breast tissue (also known as proliferative lesions) or comprised of increases in fibrous tissue, ductal enlargement, or cyst formations (known as nonproliferative lesions). Women with a history of proliferative breast lesions have an increased risk for breast cancer, particularly if the cells appear abnormal (atypical hyperplasia).
Breast density on mammography — Women whose mammograms show many dense areas of tissue have an increased risk of breast cancer compared to women whose mammograms reveal mainly fat tissue.
High bone density — Bone contains estrogen receptors and is sensitive to circulating estrogen. Therefore, bone mineral density (BMD) is considered a surrogate marker to circulating estrogen levels. In studies, women with a high BMD have a higher risk of breast cancer.
Other hormonal factors
Androgens — Elevated testosterone levels in women are associated with an increased risk of breast cancer with some studies suggesting an elevated risk specifically for hormone receptor-positive disease.
Insulin — Other hormones that may influence breast cancer risk include high levels of insulin and growth factors related to the insulin pathway.
Lots of ways to ways to get in weigh bearing exercises
Jump up and down on the spot a few times
Carry shopping one bag in each hand
carrying a baby or child is weight bearing
Lifting a heavy kettle is weight bearing
You are doing things in your life all the time that is weight bearing