On any given day, 20 percent of American children are eating pizza.

All of that pizza adds up -- it's the second leading source of calories for children, right behind sugary, grain-based desserts like cookies.

The study, released in the journal Pediatrics, used data from the National Health and Nutrition Examination survey. It tracked 11,000 children aged 2 to 11, and adolescents 12 to 19.

On the days they ate pizza, children and adolescents used a quarter of their calories on the food. This is problematic since most children don't balance pizza with more nutritious options.

Some dieticians look at this as an opportunity to introduce more vegetables to young people. When parents serve pizza, add vegetables as toppings.

It also appears the recent changes in school lunch guidelines have made the pizza children receive at school a bit healthier.

Read More:

• Your kids are getting way too many calories from pizza (Washington Post)
• This Is the Scary Amount of Pizza Kids Are Really Eating (TIME)
• 1 in 5 U.S. kids eats this food every day (Philly.com)