Honestly. It sounds kind of just like something kids do.
I know that sounds like a half ar$ed answer, but kind of like, "heehee, lets steal a muslie bar and eat it, mum will never know!" The fun of it?? and to avoid going to sleep for just that extra 10 minutes ?
Then when you confronted them, the first thing they thought of was to say you don't feed them enough, lol.

May be off track, but thats how I would interpret it