Children's exercise: 'Get moving early to stay active'
22 August 2013 Last updated at 09:11 BST
Only a third of girls aged seven are getting enough exercise, according to a study following children's activity levels.
Half of all UK seven-year-olds do not get the recommended hour of physical activity every day, but girls, children of Indian origin and those in Northern Ireland are notably less active.
Professor Carol Dezateux told the BBC the findings were particularly worrying for girls as studies show their activity levels drop as they reached adolescence.