Women in Northern Ireland are the most physically active in the UK, with just over a third getting the recommended amount of exercise.
With 35% making sure they take 30 minutes of activity daily, the province is ahead of the rest, according to a study by the World Cancer Research Fund (WCRF).
Kate Medoza, head of education at the WCRF, said: "Women in Northern Ireland are leading the rest of the UK when it comes to getting the required level of physical activity, but nationwide activity levels are worryingly low. Women need to be more physically active and hopefully the Olympics will provide a boost."
She called for changes to food labelling to make healthy eating choices easier, and said town planners should help ensure activity is safer and more attractive.
In Wales just a quarter of women get 30 minutes of moderate activity a day, with 29% in England and 33% in Scotland. Men are more active than women.
Northern Ireland has the lowest levels of childhood obesity in the UK - 27% of children aged between two and 15 are overweight or obese. Among Northern Ireland adults, 59% are overweight or obese.
After smoking, being overweight is the greatest preventable risk factor for cancer. Being a healthy weight can also help cut the risk of heart disease and some forms of diabetes.
Northern Ireland health minister Edwin Poots set 10-year targets earlier this year to tackle obesity in everybody from newborns to seniors.
He said the focus had shifted from simply trying to stop the rise in the levels of obesity, but under the Fitter Future For All strategy he wanted to reduce the level of adult obesity by 4% and the levels of those who are overweight or obese by 3%.
"This means changing for better the lives of about 60,000 people," he said in March.