Although genetics may play a large factor, women have more control over breast cancer than they think," says Margaret I. Cuomo, MD, author of A World without Cancer: The Making of a New Cure and the Real Promise of Prevention. "Everything we do from the moment we wake—from what we eat and drink to whether or not we exercise and avoid BPA, parabens, and other carcinogenic chemicals—is a factor that can turn on or off the genetic switches in our bodies, including ones that could lead to cancer. The risk of many cancers, including breast cancer, can be significantly reduced by living a healthy lifestyle."

There are also new ways to improve your risk profile, including becoming aware of the geography of your breasts and tracing your dad's family history, not just your mom's. You won't eliminate risk altogether, but you may be able to dramatically slash your chance of developing the disease. Here's where to start.

1. Find out how dense you are

One of the newest ways to protect yourself is to learn whether you have dense breasts. When you have more tissue than fat in your breasts, which is common in younger women, it makes cancer harder to detect on a mammogram: Both tumors and breast tissue show up white, while fat looks dark. Even more important, having dense breasts makes your cancer risk up to 6 times higher. Experts aren't sure why that is, but one possibility is the fact that there is no standardization for measurement of breast density, so doctors' scores are subjective.

As of this past year, at least 13 states (Alabama, California, Connecticut, Hawaii, Indiana, Maryland, New York, North Carolina, Nevada, Oregon, Tennessee, Texas and Virginia) require clinics that perform mammograms to inform patients of their breast density scores; two states (Utah and Maine) allow voluntary notification and more states are expected to follow suit. In the meantime, ask the radiologist who does your mammogram whether your breasts are dense. If your density is low, you still need regular checkups. If it's high, there's nothing you can do to lower it (though breast density does tend to decrease with age), but you can protect yourself by asking your doctor about adding MRI or ultrasound to your screening regimen, or switching from traditional mammography to digital, which is higher in contrast, making it easier to see abnormalities in dense breast tissue.

2. Get moving

Exercise seems to protect against breast cancer in several ways. First, it helps control weight. An American Cancer Society study found that women who'd gained 21 to 30 pounds since age 18 were 40% more likely to develop breast cancer than those who hadn't gained more than 5 pounds. The reason: estrogen, which can stimulate cell overgrowth and breast cancer. Before menopause, most of a woman's estrogen is produced by her ovaries; after menopause, when ovaries stop producing the hormone, most of the estrogen comes from fat tissue. The more fat in a woman's body, the more estrogen.

Second, exercise alters estrogen metabolism, according to a study published in the journal Cancer Epidemiology, Biomarkers & Prevention. "Among women who exercise, the ratio of 'good' estrogens to 'bad' estrogens [those that can damage DNA and increase a woman's breast cancer risk] improved by roughly 25%. Past research has shown that the greater this ratio, the lower a woman's breast cancer risk. Among women who don't exercise, the ratio didn't budge," says study coauthor Mindy Kurzer, PhD, a professor of nutrition at the University of Minnesota.

That doesn't mean you have to start training for an Ironman. In fact, the Women's Health Initiative found that women who walked briskly for 1¼ to 2½ hours a week had 18% less risk of breast cancer than women who were inactive. To protect yourself from breast cancer—and all cancers—the ACS recommends aiming for 150 minutes of moderate-intensity exercise weekly, which breaks down to 30 minutes 5 days a week.

3. Know your family cancer history—even your dad's

About 5 to 10% of breast cancer is hereditary, passed from one generation to the next via a variety of mutated genes. Your father's family counts as much as your mother's. And look at your family's history of other kinds of cancer, too. Men can carry some of the same aberrant genes, such as BRCA1 and 2, that up the risk of not only breast cancer but also ovarian cancer in women, pancreatic cancer in men and women, and early prostate and testicular cancers in men. Also, multiple diagnoses on either side of your family can be a clue to a hereditary link.

You may know that the medical history of first-degree relatives (parents, siblings, and children) is most important for assessing risk, but take a look at second- and third-degree relatives, too (aunts, uncles, cousins, great-grandparents, grandchildren, nieces, and nephews). If your family history worries you, enlist the help of a genetics expert. Dance instructor Suzanne Citere, 49, of Lighthouse Point, FL, examined her family history—her mother died young from breast cancer, while her maternal grandfather, maternal grandmother, and two of her mother's siblings all died from different cancers—and called a genetic counselor, who recommended testing. Citere found out that she did indeed carry a genetic mutation—BRCA2—and made the tough decision to have a prophylactic double mastectomy. People with a mutated BRCA gene are about five times more likely than other women to get cancer.

"Genetics is a very complicated topic, and genetic counselors can not only provide you with the most accurate, up-to-date information regarding your risk but also help you decide whether or not genetic testing is right for you," says Sue Friedman, founder and director of FORCE (Facing Our Risk of Cancer Empowered), a national support network for people at high risk of breast and ovarian cancers. "Then, if it is, they can also help you really understand your test results and your options based on them."