The Big Issue with Breast Cancer: How Your Weight Affects Your Risk

Weight Gain and Breast Cancer

Sometimes Tina Mitsis, 28, feels like a walking time bomb. "Both my mother and grandmother have or have had breast cancer," says Tina, a lawyer in New York City. But rather than live in fear, she's taking action to outsmart the disease. "I'm fit, I'm at a healthy weight, and I intend to stay that way," she says. Tina does cardio workouts at the gym two to three times a week, she walks 40 minutes a day, and she eats plenty of fruits and vegetables. So far, so good: For the past two years her quarterly breast exams have been clean.

Tina has discovered what more and more researchers are calling one of the secrets of preventing breast cancer: maintaining a healthy weight. The latest research shows that being overweight or obese significantly raises a woman's chances of getting the disease -- and it's often a far bigger factor than genetics. "Women think breast cancer is mainly related to family history," says Melinda Irwin, PhD, associate professor of epidemiology and public health at Yale School of Medicine. "But in truth, only about 10 percent of cases are. That means 90 percent of breast cancer may be caused by environmental or lifestyle factors like weight."

Packing extra pounds is one of the biggest risks for many types of cancer. In a groundbreaking study published several years ago in the New England Journal of Medicine, women who weighed the most died of cancer at a 62 percent higher rate than those who were slimmer. The researchers blamed excess weight for up to half of all deaths from breast cancer alone. "The scary thing is that even as more and more research shows a link between weight and cancer, women are becoming heavier and less active," Irwin says. She and other experts worry that this could lead to a rise in cancer cases down the road.

Yet for all the dire warnings, women aren't getting the message. Only 8 percent of people in the United States realize that being heavy increases cancer risk, reports the American Cancer Society; 92 percent have no idea. One reason for this: Doctors rarely discuss weight during the typical office visit. Just 11 percent of overweight patients received diet counseling from their MDs, concluded a study by Robert Wood Johnson Medical School in New Brunswick, New Jersey. "Most doctors find dealing with weight frustrating," says Jeanne Ferrante, MD, a researcher at the school who did a follow-up study on physician attitudes. "That's partly because a lot of patients don't like to talk about it. But doctors also have negative attitudes." In the study, 78 percent of doctors felt obese people didn't have enough discipline to lose weight, and 52 percent felt they weren't motivated enough.

Not only that, obese women are more likely to skip cancer screenings such as mammograms, according to research at the University of California, Berkeley. "It's a double-edged sword," Irwin says. "Women who are heavy or who gain weight up their cancer risk, but they also become less likely to get the tests they need."