Exercise 'could prevent cancer'
More than 10,000 cases of breast and bowel cancer could be prevented each year if people took more exercise, such as going for brisk walks, experts said.
Just 45 minutes a day of activity at a moderate level could prevent about 5,500 cases of breast cancer in the UK.
At least 4,600 bowel cancer cases could also be stopped if people were moderately active for at least 30 minutes a day, five days a week, research showed.
Moderate activity is any type of exertion which gets the heart beating faster and makes people breathe more deeply.
Shorter bouts of exercise are also just as effective as longer sessions - it is the total time spent on activity that is important.
The calculations, from the World Cancer Research Fund (WCRF), show the importance of diet and exercise in lowering the risk of developing cancer.
Alongside brisk walking, other activities that would count include cycling at a leisurely pace, dancing, swimming at a leisurely pace, gardening and vacuuming combined with other housework.
According to the WCRF, exercise also cuts the risk of women developing womb cancer.
And because people who exercise tend to be more likely to keep a healthy weight, their risk of dozens of other cancers is lower than people who are overweight or obese.
Health experts warned last week that obesity was placing an "overwhelming" burden on the NHS as figures showed a 785% rise in weight-loss surgery.