The number of children doing an hour of exercise a day falls by nearly 40% between the ages of five and 12. Figures suggest that by the final year of primary school, just 17% of pupils are doing the recommended 60 minutes of physical activity every day.
A spokesman for Public Health England described the drop in activity levels as "concerning".
More than a third of children in England are overweight by the time they leave primary school.
A new survey from Public Health England and Disney looked at the effects of physical activity on children's emotional wellbeing More than 1,000 children aged five to 11 were questioned, with their parents acknowledging that being active made their children feel happier (79%), more confident (72%), and more sociable (74%).
But the survey also found that children's overall happiness declined with age, with 64% of five-and six-year-olds saying they always felt happy, compared with just 48% of 11-year-olds.
