The study, published in the British Journal of Cancer today, claims men who watch less than an hour of television a day are 35% less likely to develop the disease than peers sitting through more than four hours of programmes.
Data from almost 500,000 men and women between 2006 and 2010 was analysed to investigate a possible link between sedentary behaviour and the risk of developing bowel cancer.
It found men who spent less time in front of the TV were also less likely to develop bowel cancer later in life.
After six years of follow-up 2,391 people from the UK Biobank study went on to develop bowel cancer.
When researchers from the International Agency for Research on Cancer (IARC), Imperial College London and the University of Oxford analysed the data they made the link between sedentary behaviour and bowel cancer.
The study also revealed an increase in physical activity was associated with lower colon cancer risk in men.
However, despite apparent similarities they found no link between computer screen time and an increased risk of bowel cancer.
Dr Neil Murphy, lead researcher based at the IARC in France, said: “Previous research suggests that watching TV may be associated with other behaviours, such as smoking, drinking and snacking more, and we know that these things can increase the risk of bowel cancer.
“Being sedentary is also associated with weight gain and greater body fat.
“Excess body fat may influence the blood levels of hormones and other chemicals which affect the way our cells grow, and can increase bowel cancer risk.”
Bowel cancer is the third most commonly diagnosed in UK men, and there were around 41,800 new diagnoses in men and women in 2015 alone.
Professor Linda Bauld, Cancer Research UK’s prevention expert, said: “This study poses interesting questions such as why screen time from computers didn’t increase the risk of bowel cancer but watching TV did.
“There is evidence that greater exposure to TV junk food adverts increases the likelihood of eating more, which will also increase your chances of becoming overweight.
“It’s interesting that only men who watched a lot of TV had an increased risk of bowel cancer, but not women.”
She said: “The study didn’t look at this directly, but it could be because men might smoke, drink and eat more unhealthily than women while watching TV.
“We’ll need further research to answer the questions this study raises. What we do know is that keeping a healthy weight, cutting back on alcohol, being physically active and eating a diet rich in fruit and vegetables are known to cut your risk of bowel.”
Dr Lisa Wilde, director of research and external affairs at Bowel Cancer UK and Beating Bowel Cancer, added: “This study adds to the substantial evidence that bowel cancer could be prevented by leading a healthier, more active lifestyle.”
