Avoiding these behaviors helps reduce your risk. Evidence suggests that fat plays a role in the development of breast cancer. Studies have also linked high-fat diets to ovarian, prostate and colon cancers, which, like breast cancer, are affected by hormones. Foods that are high in fiber, such as beans, bran, whole grains, fruits and vegetables, help prevent breast cancer by removing excess estrogen from the body or reducing estrogen's activity. They also reduce the risk of heart disease and colorectal cancer.
Smoking is known to cause lung cancer, and new evidence also links it to breast cancer.
One study of 3,200 women found smokers were 60 percent more likely to develop breast cancer than nonsmokers. Excess weight is linked to breast cancer because extra fat tissue produces more estrogen, which increases the level of available estrogen in the body. Excess fat also causes your body to metabolize estrogen less efficiently. One study of 1,000 women under age 40 found those who exercised at least four hours a week lowered their risk of breast cancer by 60 percent. Those who worked one to three hours a week lowered their risk by 30 percent.