Don't sit there, move! In a widely publicized Norwegian study involving more than 25,000 women, those who exercised vigorously cut their cancer risk by more than a third compared to non-exercisers. [New England Journal of Medicine, May 1, 1997] If you have a desk job, exercise may be extra important. This year, Swedish researchers reported that women who had sedentary occupations during their reproductive years and lacked leisure-time physical activity had three times the risk of breast cancer compared to those physically most active both inside and outside the workplace [Cancer Causes Control, July, 2000]. One explanation is that exercise may stimulate the immune system or fight free radicals that corrode cells, suggests Dr. Cohen.