Exercise

A good, sweaty workout — or even a relatively light, leisurely one — lowers your risk of obesity and may help prevent cancers of the breast and colon. The exercise doesn’t have to be intense to provide some benefit: Women who walked briskly for 1 1/4 to 2 1/2 hours a week reduced their risk of breast cancer by 18 percent, according to the Women’s Health Initiative Cohort Study, published in 2003.

Scientists aren’t sure how much exercise is optimal or exactly why it’s effective, but more and more studies are confirming the ability of exercise to prevent cancer — and that goes beyond breast and colon cancers, according to Grover Bagby, M.D., the director of the Oregon Health & Science University Cancer Institute, in Portland.

What to Do: The National Cancer Institute (NCI) recommends at least 30 minutes of moderate physical activity (such as brisk walking, swimming, dancing, or lawn mowing) five days a week, or 20 minutes or more of vigorous activity (such as jogging, high-impact dancing, swimming continuous laps, or biking strenuously) three or more days a week.

Practice Safe Sex

“Most people don’t think of safe sex as an important step for cancer prevention, but it is,” says Carolyn Aldigé, the president and founder of the Cancer Research and Prevention Foundation, in Alexandria, Virginia.

Two types of the human papillomavirus (HPV), a sexually transmitted disease, are responsible for most cases of cervical cancer in the United States, according to the American Cancer Society (ACS). Scientists believe the virus causes inflammation that can lead to cervical cancer, which kills about a third of women diagnosed with it. HPV spreads by sexual contact and usually has no symptoms, so a woman can have the virus for years without realizing it.

What to Do: Get regular Pap smears, which are the best way to detect precancerous or cancerous cells of the cervix caused by HPV. Ask your doctor about a new vaccine called Gardasil, which may protect women from the two most common cancer-causing strains of HPV and prevent up to 70 percent of all cervical cancer cases. The most recent study of the vaccine showed that all women who were vaccinated were cancer-free more than four years later. It’s the first vaccine ever developed to prevent cancer, and it may become available this year.

Stay Slim

Obesity increases the risks for all sorts of cancers, including cancer of the breast, uterus, kidney, pancreas, and colon. “When you’re 20 percent over your ideal body weight, that’s when you begin to see increased risk, and it continues to increase with every pound gained,” says ACS president Carolyn D. Runowicz, M.D.

There are a number of theories as to why. One is that obesity boosts estrogen levels in women, raising the risk of hormone-related cancers, such as breast and endometrial. Another is that obesity elevates insulin levels, stimulating cell growth and contributing to diabetes, which is linked to liver, colon, and pancreatic cancers. Scientists at the Mayo Clinic Cancer Center in Rochester, Minnesota, have found that the risk of developing pancreatic cancer within three years of a new diabetes diagnosis jumps eightfold.

What to Do: To determine whether your weight puts you at risk, give yourself a virtual weigh-in with the body-mass-index calculator. A score of 18.5 to 24.9 is considered normal; 25 to 29.9 is overweight; and 30 or more is an indication of obesity and a higher cancer risk.