It is legal to sell unhealthy food, ie poisonous food. Sugar is a poison, drugs are poisons. You can legally sell escolar a fish that if eaten too much is poisonous.
What is poisonous food? You can sell plastic that breaks down into the environment and people are drinking it in water, eating it in fish. Is that legally sold poisonous food?
Sugar is not poison. It can be, in certain situations, "bad for you". But sugar is found naturally in a variety of fruits and vegetables and has been a staple of the human diet for all of history and pre-history. There's no way to describe it as "poison".
What is poisonous food? You can sell plastic that breaks down into the environment and people are drinking it in water, eating it in fish. Is that legally sold poisonous food?