Can lifestyle choices help prevent breast cancer in women who are genetically predisposed? Now there is more evidence to suggest the answer is yes. A recent study found that women ages 18 to 30 who carry a BRCA1 gene mutation can reduce their risk of early-onset breast cancer by as much as 65 percent by losing at least 10 pounds Breast Cancer Research, 2005, vol. 7, no. 5). "The maintenance of a healthy weight during early adult life represents a potentially modifiable risk factor in hereditary breast cancer syndromes," says one of the study's lead scientists, Steven Narod, MD, of the Centre for Research in Women's Health at the University of Toronto.

Many of the study participants who lowered their risk by losing 10 pounds or more were considered overweight based on their body mass index (BMI) at age 18. Therefore, the study suggests that young women whose BMI is above 25 would be wise to lose weight, especially if they have a known mutation. Women with a BMI of 18.5 to 24.9 are considered of normal weight, while those with a BMI of 25 or more are considered overweight. Weight loss after age 30 did not have the same effect.

Approximately 10 percent of breast cancer cases can be attributed to either the BRCA1 or BRCA2 genetic mutations, and women who inherit either one of these breast cancer susceptibility genes have a lifetime risk of 45 percent to 87 percent for developing breast cancer. However, "just because it's genetic doesn't mean you can't do anything about it," encourages Narod.