Increasing the number of young children who exercise for just under a half hour a few times a week could save tens of billions in medical costs over their lifetimes, researchers said Monday.
Currently, just 32 percent of US children aged eight to 11 get enough exercise, said the report in the journal Health Affairs.
The minimum guideline of 25 minutes a day, three days a week, was established by the Sports and Fitness Industry Association.
But if even just half of children exercised that much, the nation could avoid $21.9 billion in medical costs and lost wages over the course of their lifetimes, said the report by researchers at Johns Hopkins University's Bloomberg School of Public Health.
And if 100 percent of all kids in that age range did, $62.3 billion could be averted and 1.2 million fewer youths would be overweight or obese.
"Physical activity not only makes kids feel better and helps them develop healthy habits, it's also good for the nation's bottom line," said lead author Bruce Lee, executive director of JHU's Global Obesity Prevention Center.
"Our findings show that encouraging exercise and investing in physical activity such as school recess and youth sports leagues when kids are young pays big dividends as they grow up."
- Obesity rates -
About one in six US youths aged two to 19 are overweight or obese, according to the US Centers for Disease Control and Prevention.
The CDC defines being "overweight" as having a body mass index -- a ratio calculated using measures of height to weight -- that is between 25 and 30.
Being "obese" means having a BMI higher than 30. The normal BMI range is 18.5-24.9.
More than one in three US adults are obese (36.5 percent), raising their risk of heart disease, stroke, diabetes and other life threatening conditions such as certain cancers.
Research has shown that youths who are overweight by age 18 are far more likely than normal-weight peers to be overweight as adults.
The study also looked at the possibility of no change, with just under a third of kids aged 8-11 continuing to meet the three-times-a-week exercise guideline.
"Maintaining the current level of physical activity would result in 8.1 million of these youths being overweight or obese by 2020," said the study, anticipating "$2.8 trillion in additional medical costs and lost wages over their lifetimes."
The lifetime medical costs for a person who is overweight average $62,331, while lost wages average $93,075, according to the study.
For people who are obese, the costs are even higher.
"As the prevalence of childhood obesity grows, so will the value of increasing physical activity," said Lee.
"We need to encourage kids to be active, to reduce screen time and get them running around again."