parents also seem to believe that they have to persuade or force their children to eat
They do? I would be very surprised at parents who believed this. Eating satisfies a natural desire and feels good. Sleeping means stopping the fun thing you're doing and lying down in a dark room; why would kids want to do that?
I have two kids. If left to their own devices, they would eat the tastiest things on their plate, then stop (then complain about being hungry an hour later). They would never eat anything remotely healthy, and subsist entirely on chocolate if given the choice.
Since we have evolved to value fat and sugar as being the tastiest substances, children do have to be taught/persuaded to eat healthy food.
They also do need to be told when to go to bed. The times at which we have tried to let them set their own bed times have resulted in them trying to stay awake as ...
Full essay: http://www.gwern.net/Melatonin