"When you're obese, you have higher insulin levels, which promotes cancerous cell growth," explains review author Anne McTiernan, M.D., director of the Prevention Center at the Hutchinson Center. Another explanation for poor survival rates: Almost 40 percent of severely obese women get a significantly lower dose of chemo than they need, according to research at the University of Rochester. "The heavier you are, the more chemo you need to wipe out cancer — and some physicians are scared to give such massive doses to patients," says Griggs, who authored the study.

However, there is some reassuring news for those who are heavyset: Losing weight at any age can help cut breast cancer risk. Findings in the Journal of the American Medical Association reveal that postmenopausal women who lost 22 pounds were 57 percent less likely to develop the disease compared with those who maintained their weight.

Women on a Low-Fat, Veggie-Rich Diet Are Safer from Breast Cancer

There's been a lot of conflicting research on diet and breast cancer risk, but the latest findings suggest that following a low-fat diet and eating plenty of produce can help prevent the disease. Earlier this year, a National Institutes of Health study found that postmenopausal women who got 40 percent of their calories from fat were 11 percent more likely to get breast cancer than women who got 20 percent of their calories from fat. And eating ample fruits, veggies, and whole grains lowered women's risk by 17 percent in one French study.

A low-fat, veggie-rich diet also seems to help prevent breast cancer recurrence.

Women with early-stage breast cancer who consumed less than 33 grams of fat daily slashed their odds of recurrence by about 24 percent in one NCI study. And new research found that eating at least five servings of fruits and veggies a day (and getting three hours weekly of moderate exercise) can cut in half your risk of dying from breast cancer.

"We know that a high-fat diet boosts hormones that promote cancer cell growth," explains McTiernan. And a low-fat diet also fends off the extra pounds that boost breast cancer risk. As for fruits and veggies, "the more you eat, the greater your chance of consuming more cancer-fighting antioxidants and phytochemicals," explains Jennifer K. Reilly, R.D., senior nutritionist for The Cancer Project, a nonprofit consumer-education group in Washington, DC.

Women Who Exercise Are Less Likely to Develop Breast Cancer

Like it or not, exercising regularly is one of the best ways to both prevent breast cancer and survive a diagnosis. And you don't have to expend much energy to get some benefit — just 1.3 hours weekly of moderate activity lowered women's risk of developing the disease by 20 percent in one University of Southern California study. The same goes when it comes to beating the disease: A Harvard University study of almost 3,000 women with breast cancer found that those who did the equivalent of walking just an hour a week at a pace of 2 to 3 mph reduced their risk of death by 20 percent.

Exercise packs a lot of powerful anticancer punches: It reduces levels of circulating estrogen, which feeds hormone-sensitive tumors; it lowers levels of insulin, a hormone linked to recurrence; and it helps you drop the extra pounds that up your risk. Simple exercises like Walking is the easiest way to get moving, so consider buying a pedometer: Omron HJ-112 Digital Pocket Pedometer Simply clipping one on has been shown to motivate all women to sneak in more steps each day, and a University of Alberta study found that breast cancer survivors who received a pedometer increased their exercise by almost 90 minutes a week, compared with a 30-minute increase a week among those who didn't get one. So take a step in the right direction for your health.