If your child is fat it could have more to do with how much time they spend behind a screen rather than how active they are.
Queensland researchers have studied the habits of 144 kids, with surprising results.
They looked at the children's level of physical activity, body mass index, and how much time they spent staring at screens, from computers to TVs and video games.
And physical activity was not the deciding factor in whether a child was overweight or not.
"Most of the children were reasonably active and overall did similar levels of physical activity, which had no direct correlation with their weight," says Dr Rachael Sharman, from the University of the Sunshine Coast.
"However, those who were overweight spent significantly more time sitting watching television or playing computer games than those in the normal weight range."
She said the study, which looked at kids aged five to 13, showed how important it was for parents to limit screen time.
"Parents need to encourage and support children to be physically active but they also need to set limits for screen time to ensure the benefits of physical activity aren't negated by too much time spent sitting."
The study also found kids who were involved in sport at a club or team level were less likely to trade off physical activity for screen-based activities.
Dr Sharman will present her research at the Australian Psychological Society Conference in Cairns on Wednesday.