Taking exercise can cut the risk of the most common kind of bowel cancer by a quarter, research suggests.
US scientists, who reviewed 52 previous studies, calculated the most active people are 24% less likely to develop colon cancer than the least active.
Colon cancer is the most common form of bowel cancer, a disease which affects more than 36,500 people a year in the UK, causing 16,000 deaths.
The study appears in the British Journal of Cancer.
The study took into account many different types of physical activity including occupational activity like manual labour, as well as more traditional leisure-time activity such as running or going to the gym.
Lead researcher Dr Kathleen Wolin, from the Washington University School of Medicine in St Louis said: "These results give us a very reliable calculation of the positive effect that exercise can have on reducing colon cancer risk.
"It's very positive to see that exercise has such a clear benefit in reducing cancer risk and we hope it will encourage people to enjoy a healthy active lifestyle as well as treating it as a way to minimise their colon cancer risk."
Dr Wolin said she hoped it would eventually be possible to give individuals a detailed breakdown of how they could reduce their chances of cutting their risk of bowel cancer tailored to their own specific circumstances.
Sara Hiom, director of health information at Cancer Research UK, said: "One hundred people a day are diagnosed with bowel cancer in the UK alone, so it's imperative that we do all we can to prevent the disease.
"We know that around half of all cancers could be prevented by changes to lifestyle.
"Maintaining a healthy bodyweight is one of the best ways to lower the risk of bowel and other cancers - potentially helping to avoid an estimated 13,000 cases each year."