Even a small improvement in fitness helped, the researchers found. For instance, a 50-year-old man who increased fitness so he could last three more minutes on the treadmill, Lakoski said, could reduce cancer death risk by 14 percent and heart disease death risk by 23 percent.
Low fitness levels increased the risk of cancer and heart disease even in men who weren't obese, the researchers found.
They also took into account other factors that could increase risk, such as age and smoking habits.
The good news, Lakoski said, is that, "You don't have to be highly fit to get protection." The most protection against cancer and heart disease was found in moving out of the least fit group.
And how unfit were those men? The men in the least fit group who were 40 to 49 when they took the test could walk on the treadmill less than 13.5 minutes. Those who were 50 to 59 lasted less than 11 minutes. Those 60 and older in the least fit group only lasted less than 7.5 minutes.
The findings make sense, said Colleen Doyle, director of nutrition and physical activity for the American Cancer Society.
"While you can't tell just how much activity these guys were doing over time, it makes sense that the most fit would have better cancer-related outcomes -- because they are likely the most active." While the new research did not find a link between fitness levels and a diagnosis of prostate cancer, a recent review of other published studies did show a modest reduction in that risk, Doyle said.
Lakoski can't explain the protective effects of fitness for sure, but can speculate. "We know that fitness modulates several important pathways also related to cancer risk," she said. These include, among other path
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