The market is incapable of self-regulation, that much has shown itself to be true. Removal of marketing towards children and easy access to vending machines will go a long way in improving public health in Australia. The days of avoiding a nanny state in Australia are pretty much gone, the government regulates everything, and for the most part it hasn't actually been bad at all.
> but they need to pay their own healthcare costs somehow.
Terrible idea, Medicare is one of Australia's shining institutions (even with all it's bureaucratic flaws). The American healthcare model has literally 0 chance of ever being adopted in Australia. The simple fact is we live in a socialised society, and so when burdens are placed on the public infrastructure from profit hungry corporations, the natural response is to regulate and deal with it. We saw it with cigarettes, hopefully we see it with sugar, and one day with alcohol too.