Now I know.
Childhood obesity is partly caused by sleep deprivation, according to new research from the University of Bristol in England.
Apparently, lack of sleep triggers hormonal changes in children and teenagers which cue the body to eat sugary and starchy food to provide an energy boost.
Furthermore, children are likely to sleep less if they are not active during the day. This fact compounds the problem of weight gain. Not only are children burning off insufficient calories during the day, they are then sleeping less at night and eating more of the wrong food to make up for this.
"Drastic measures" are apparently needed to halt this growing epidemic - which sounds like a pretext for another expensive government initiative.
Personally, we've always believed that children should play outside a lot. The street is safe enough if you train children to be aware of the dangers. Mine all have energetic lives and sleep like troopers. This, combined with a normal diet, has so far kept them right on the numbers with their Body Mass Index.
As a piece of encouragement for concerned parents everywhere, I submit a short clip of my son and a friend doing their bit to battle the obesity crisis. May I present a new Atlantic World production - Boys Jumping off a Piano.