The people could also just eat healtier, right (if they can afford it, that is)?

"All things are poison and nothing is without poison, only the dosage makes a thing not poison."

But I guess if sugar etc. would get a high tax, the tax money could be used to better educate the people which could possibly turn them away from too much sugar. And if we are at it, remove mc donalds, burger king etc. from the school grounds and sell healtier food.