How many calories?

Last night our church had a potluck dinner to celebrate Christmas. After all the eating was done (way too much by yours truly) all the tables and chairs were cleared from the sanctuary, and kids started running in circles in the big open spaces.
After running for a few minutes, Kyle came up to me, puffing and hot from all the running and asked how many calories he had burned off. My answer "more than 10" didn't satisfy him - he wanted to know the actual number... So, I had to say "I don't know - you don't have a calorie counter on your forehead." Some of the other parents near by though that was immensely funny...