Fewer than half of Northern Ireland's children are doing enough exercise, it has been revealed.
Despite this most parents think they are active enough, a survey showed.
Around a fifth of boys and 15% of girls are overweight or obese, the British Heart Foundation in Northern Ireland added.
The charity published a report, Couch Kids, highlighting the need for more activity.
Associate medical director Dr Mike Knapton said: "Mums and dads need to take off the blinkers about how active kids need to be in order to keep their hearts healthy.
"Kids need to get moving yet we have been standing still for the last decade."
Around 44% of children are doing the recommended daily hour of physical activity.
Mr Knapton added: "Parents have such an important role in helping and encouraging their kids to be more active by building exercise into their everyday lives - whether that's taking part in team sports, playing outside with their friends or walking to school."
The UK-wide report collected research from a wealth of sources to provide a clear picture of the level of childhood obesity, how active children are, barriers that stop them from exercising, and made recommendations on tackling the problem.
Dr Knapton added: "Public health needs to feature more strongly in transport, planning and education policies. One example would be through recognising the importance of safe cycling routes and making sure children have interesting places to play."
The charity called for consistent guidelines on recommended levels of physical activity for all age groups.
It urged schools to maximise the opportunity for children to enjoy activity during and around the school day and called for consistent collection of data on exercise levels.
© Press Association