The primary problem that most people have with Mayor Bloomberg’s ban on large sodas (and the ACA for that matter) is that it turns the state into a “nanny.” The problem with that argument is primarily that the state already does that.
Common examples include things like seat belts for the driver. Most people agree that this is a good idea, but at its core, the goal is simply protect a person from themselves. There is no “public” interest that has to be protected, just the people from themselves.
The problem is that people have a terrible idea of what is good for them, and more specifically they have consistent problems thinking for the long term. When this manifests itself in the savings rate, credit card debt, and seat belts for that matter, the state steps in (as much as legislators are comfortable with anyway) and they protect people from themselves.
The case of health insurance and the soda ban is even more clear than the above examples. In these cases, the government the government is not only protecting people from themselves (people in the aggregate, not necessarily every individual) but people from other people. Assuming that soda really does make people obese (which seems to be well documented (cited by 1670)) it has real costs to society. Since many people that are obese are concentrated in the lower economic strata, Medicaid, and Social Security disproportionately have to pay for the additional treatment that is required.
The money does not come out of the ether. It comes from people’s pockets that are not obese, as well as those that are (and disproportionately those that are not). To claim that the state should both pay for treatment for a large number of self-inflicted ailments (again, in the aggregate) at the same time as tying its hands for fixing the root cause is absurd (a legitimate point of view is to say that the government should do neither of these things, but that view gets much less popular support).
To the claim that the government could pass a law that says that people have to eat an apple a day, I have one response: Don’t elect such people