Where do little children get so much energy from?!?

I mean, they eat so little as compared to adults, yet they remain indefatigable!!! If you don't believe me...let me tell you what I've seen :) On a seven-hour train journey recently, I found most adults drooping and wilting while children's energy, verve and chatter remained quite unaffected... show more I mean, they eat so little as compared to adults, yet they remain indefatigable!!!

If you don't believe me...let me tell you what I've seen :)

On a seven-hour train journey recently, I found most adults drooping and wilting while children's energy, verve and chatter remained quite unaffected till the very end!

What is their secret, according to you?

Thanks :)
Update: @ George: I do run in circles...but seldom when my mind and body are at ease ;))
Update 2: @ Phil: Those children ranged from 4 to 10 years! Very active and alert...both mentally and physically...none too overweight or over-interested in food, except for the ice-cream :) And, this happened both times...while going and coming, with different sets of children!
Update 3: @ Spiritualseeker: Its true that they weren't "lost" in thoughts...they were perpetually 'presenting' thoughts as they arose. In a mean way ;) I think 'nameless' is correct....they were drawing energy from their parents' answers...chewing and spitting fresh set of questions... show more @ Spiritualseeker: Its true that they weren't "lost" in thoughts...they were perpetually 'presenting' thoughts as they arose.

In a mean way ;) I think 'nameless' is correct....they were drawing energy from their parents' answers...chewing and spitting fresh set of questions at them, lol...sometimes just playing among themselves!

A truly lively bunch that I paid covert attention to...quietly observing them from under my closed eyes :)
Update 4: Agreed, okei, love and friendships are alternate sources of energy :))
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