When Felice Austin was just 11 years old, her mother died from breast cancer. That started Austin on a lifelong campaign to lower her risk of the disease that strikes nearly 200,000 women every year.
Today, Austin, a 31-year-old mother who lives in Los Angeles, is a vegetarian who eats organic foods. She's also an avid exerciser, doing aerobic activities like biking, roller skating and surfing along with lifting weights at least five days a week.
"I know there are other benefits to exercise, but I also know that a lasting commitment to regular exercise is the best way to reduce my chance of developing breast cancer," she says.
Austin is indeed correct. In fact, a study sponsored by the World Cancer Research Fund and the American Institute for Cancer Research found that exercising more, eating healthier and keeping weight in check could prevent as many as 38 percent of breast cancer cases in the United States.
Boosting the benefit
But for many women, the big questions are: How much exercise do you need to get and what type offers the best protection against breast cancer? Fortunately, recent research has provided some of those answers, even revealing what age you should ramp up your exercise regimen to maximize the protective benefits.
In one recent study from Medicine & Science in Sports & Exercise, researchers examined cardiovascular fitness in more than 14,000 women with no history of breast cancer. Overall, women who were moderately fit, meaning that they did moderate-intensity exercise like brisk walking 150 minutes per week or vigorous aerobic activity like jogging for 75 minutes each week, had a one-third lower risk of developing breast cancer.
"Regular physical activity may be beneficial through several biological mechanisms,” says Steven N. Blair, lead study author and professor of exercise science at the University of South Carolina in Columbia, S.C. That includes reduction in hormone levels, improvements in insulin, less fat and better immunity.
The value of getting moving also got a push from a major study last year in the journal Breast Cancer Research, which followed more than 30,000 women for 11 years.
Lean women who did vigorous activity several times a week over their lifetime — such as scrubbing floors, running, competitive tennis, aerobics, bicycling on hills and fast dancing — were 30 percent less likely to develop breast cancer than women who never got their heart pumping. The same effect wasn’t seen among overweight women, a puzzler for researchers, who say, no matter your weight, any activity is better than none.
"A sedentary lifestyle is a risk factor for breast cancer, even among women who aren't overweight," says Dr. Michael F. Leitzmann, a professor of epidemiology and preventive medicine at Regensburg University Medical Center in Regensburg, Germany.
More from TODAY.com
Hillary Clinton: Granddaughter led me 'to speed up' political plans
- Lauren Hill, inspirational college basketball player, dies
- Marathon dad's victories help raise money for son with spina bifida
- Will it work on Vale? Savannah tries tissue sleeping trick at home
- Listen to the chilling 911 call Sandra Bullock made during break-in
- Hillary Clinton: Granddaughter led me 'to speed up' political plans
That’s why the American Cancer Society recommends doing at least 30 minutes of moderate to vigorous physical activity five or more days a week. Of course, more is better, which is why the group says 45 to 60 minutes a day is preferable.
The group defines moderate activity as the equivalent of a brisk walk, including things like walking, bicycling and mowing the lawn. Vigorous activity, on the other hand, should cause deeper, faster breathing and sweating and might include jogging, playing tennis, jumping rope and even weight training.
Although there aren't studies to show that strength training can reduce the risk of breast cancer, studies have found that strength training may help breast cancer survivors reduce the risk of side effects from breast cancer treatments, including lymphedema.
Never too late
Perhaps the best news from the latest research is it's never too late to start exercising to lower your risk. That's the message from a study presented at the American College of Sports Medicine's annual meeting in May in which researchers asked more than 4,000 women to recall exercise patterns in four stages of their life: 10 to 15 years old, 15 to 30 years old, 30 to 50 years old, and over 50 years old.
Although exercising before the age of 30 didn't alter the odds of developing breast cancer, women 30 years and older who exercised more than 60 minutes a week significantly cut their risk.
Video: Elizabeth Hurley and Evelyn Lauder on the fight vs. cancer "Although we don't know exactly why, exercise seems to have a protective effect for women in this age group," says Lisa K. Sprod, study author and research assistant professor in the department of radiation oncology at the University of Rochester Medical Center in Rochester, N.Y. Overall reduction in body fat may play a role, she suggests.
The message, of course, is clear: If you want to reduce your risk of developing breast cancer, add exercise to your life, no matter what your age. And don't get hung up on how much you're doing. Just get out there and move, as some activity is always better than none.
As for Austin, her mission will continue, especially now that she's a mother of an almost 3-year-old daughter. "I'm even more motivated to do everything I can to prevent breast cancer because I don't want my daughter to grow up without me," she says.
Karen Asp, a freelance journalist who specializes in fitness, health and nutrition, is a contributing editor for Woman's Day and writes regularly for Self, Prevention, Real Simple, Women's Health, Shape and Men's Fitness.
© 2013 msnbc.com. Reprints