Also they could put big taxes of all unhealthy foods, and then instead of just keeping those taxes they could funnel that cash directly back into lowering the price of healthy foods.
I actually thought about that. The problem is how would they classify food as unhealthy and where would you draw that line?
Remember that everything is toxic in certain amounts,
even water. And it's really difficult to simply count calories and stuff, since you could just limit your calorie intake. Even fast food burgers like a Big Mac actually aren't that much worse for you than other foods. It's just that it's not satisfying for its calories so most people eat it with a side of fries, a Coke, and chicken nuggets. Well now you've taken a Big Mac (570 Cal) and made it into 1830 Cal with more than your daily recommended intake of each fat, carbs, sodium, and sugar in a single meal.