Weight loss and physical health relegated to the world of business?

OK, I don't have the time to explore this issue fully, but the question has crossed my mind a number of times:

"Why has weight loss, nutrition and general physical health become the domain of business and not public, freely available, information?"

Everywhere I go there are adds for losing weight... "I cut down 10lbs of stomach fat in just 1 week by obeying this 1 Easy Diet Rule".  or improving your appearance.  "You too can have biceps like Arnold if you buy my book.."

But why do I have to pay for this information?  Why doesn't our education system take care of this for us?  Why don't our governments provide this information for free?

It's counter-intuitive.  A healthy society is a productive society.  Isn't the measure of a country's success its GDP?  Won't healthier people produce more and thereby increase GDP?

I can understand that the "health industry" has become big money -- but why do we allow this?