the fact is that many people in today's society do not have sufficient knowledge or education to understand what constitutes a healthy diet for their children
With respect, bolleaux. Very, very few people in today's society do not have sufficient knowledge or education to understand that, in the UK at least which is what I suspect you are referring to. Or in any developed society with an education system.
Indeed, lack of education - as seen in the third world, ie NO education - and lack of obesity seem to go together, don't they? I wonder why?
In the UK people eat junk food and lots of it because, so far as 99% of them are concerned, they are stupid, self-indulgent, lazy, and can always blame someone else.
They know perfectly well that this and lack of any exercise is making them what they are. But they don't give a toss. Look around in Tesco at the huge bottoms behind the fullest trolleys, and look at what's in those trolleys. And then realise that the person with that bottom can read, write, watch TV and has had at least 10 years education.