The other side of expensive food is, of course, greater consumption of cheap crap food that brings its own problems at the healthcare end. I am sure it is a very elastic equation.

One key factor to remember in deciding progressive use of taxes of any kind is that while they are designed for one frame of mass mind, the change itself will cause another frame of mass mind. This always reminds me of Mr Hulot in Mon Oncle, struggling to right a perfectly manicured bush that has lost a branch to the activities of his nephew :-)

You can't be me, I'm taken