I don't know if we should or shouldn't but it deserves more thought than you're giving it. For one thing, I seriously doubt prohibition could ever be political

I don't know if we should or shouldn't but it deserves more thought than you're giving it. For one thing, I seriously doubt prohibition could ever be politically viable, but increased prices or reduced visibility and availability of processed high-calorie ready-to-eat foods might be in some situations. We've already seen some of this, like New York's soda tax or banning vending machines from public schools.