"The current recommendations from the American Cancer Society emphasize a physically active lifestyle and the prevention of overweight/obesity," the study's lead author, Dr. Kelly R. Evenson, told Reuters Health. "Our results support those recommendations."
The findings are published in the February issue of the journal Medicine and Science in Sports and Exercise.
The study included 2,585 women and 2,890 men who were followed from the early- to mid-1970s to 1998. At the start of the study, volunteers performed a treadmill test to measure their heart health and had their body mass index, or BMI, measured. BMI is a measure of weight in relation to height used to gauge obesity.
After taking into account factors that could influence health, Evenson's team found that the fittest men were about half as likely to die from cancer as less fit men. Fitness levels did not have a significant effect on cancer deaths in women, however.
Evenson's team did not examine how fitness and obesity may affect the odds of dying from cancer, but physical activity is believed to reduce cancer risk by influencing levels of certain hormones and growth factors, by decreasing body fat and possibly by enhancing the immune system.