A new study has found that almost 40% of the Irish population is overweight.
The Slán survey of lifestyle, attitudes and nutrition also shows that 23% of people are classed as obese.
It is estimated that our physical inactivity is costing the country €1.6bn a year in health supports to treat obesity-related diseases.
Manager of the Nutrition and Health Foundation Dr Muireann Cullen told delegates at the organisation's third annual conference that inactivity was a key factor in the survey's results.
"A major factor contributing to this is the fact that 59% of adults do not meet the Department of Health’s recommended levels of physical activity, according to the same survey," she said.
"Ireland has one of the highest rates of childhood obesity in the world with 10% of children aged five-12 in this category," she added.