[asdfasgasdgasdg]

The idea that it is possible for them to control the nutritional composition of food and the balance consumed is absurd at face value.

It doesn't seem that absurd to me. If the government banned the production and import of potato chips, you could still make them at home, but people would probably make a lot less of them. Unlike drugs, food is not conveniently hidden and the value is too low per unit volume to justify illicit production. Therefore food which is banned generally will not be produced at scale.

If the government did set out to materially improve the dietary habits of the citizenry, it would definitely be possible. It would be politically infeasible and possibly tyranny, but it would be very doable.

[s1artibartfast]

I meant the word can in the context of a free society, with practical constraints.

I agree that if you ignore the constraints it would be trivial. There are so many brutal and oppressive solutions it isn't even worth listing examples.

[asdfasgasdgasdg]

I honestly think you're overstating it a little. For example there are places where foie gras is banned. I would not characterize it as brutal and oppressive. I guess there are some libertarians who would say oppressive is the proper word, but surely we can agree that brutal is a step too far?

Such a program could be done as a rachet, similarly to how tobacco use was driven to the margins.