Lack of exercise has led to 1,500 cases of cancer and 500 deaths from the disease over five years, doctors revealed yesterday.
The impact of 'couch potato' lifestyles among the population between 2011 and 2015 was analysed and women were found to be most affected.
They accounted for 1,000 cancer cases and 300 of the deaths.
The findings, by researchers led by Dr Desmond Hickey of the Health Protection Surveillance Centre and the HSE's National Cancer Control Programme, were presented to the Faculty of Public Health Medicine at the Royal College of Physicians in Dublin yesterday.
The study showed the main forms of the disease linked to inactivity were bowel, breast and womb cancer.
It is now known that being overweight or obese can lead to an increased risk of cancer.
Chronic inflammation can raise the risk and women who have higher oestrogen levels have an even greater chance of getting the disease.
The conference was told there are around 22,000 invasive cancers and 9,000 deaths from the disease annually in Ireland and it has been estimated that the numbers could double by 2045.
"Cancer prevention has been highlighted as a key priority.
"It is known that inadequate physical activity is an important preventable risk factor for cancer," the researchers said.
They urged that the findings should be used to target strategies aimed at reducing the cancer burden in Ireland.
"Policy makers and the public must be made aware of the potential to prevent cancer through physical activity," they added.
A separate study led by UCD's School of Medicine looked at the impact on people who participated in the Bowelscreen national screening programme, aimed at picking up people at risk of bowel cancer, who got a false positive result.
These would have shown positive for abnormalities in the initial FIT test. But a later invasive diagnostic procedure, a colonoscopy, showed no evidence of malignancy.
A retrospective cohort study was conducted using data from the first two rounds of BowelScreen.
The study shows a significant reduction in re-attendance rates for clients having a false-positive FIT result.
The researchers said that gastroenterologists giving colonoscopy results need to be aware they need to emphasise the importance of regular FIT tests after a negative result showing the patient has been given the all-clear.
They said letters sent to people who have had a negative colonoscopy will be reviewed. This is to ensure that they will attend for screening when they are invited again.
Eligible people are invited for screening again every two years.