It's nearly universally accepted that minors lack the ability to fully realize what their choices entail, e.g. juvenile court, age of consent. Applying the same rules to minors and adults is not a good solution.
I'd argue in the face of multi-billion dollar marketing and truthiness by Big Food (e.g. creative ways to include sugar on a list of ingredients to distort the volume of its content) , that many adults also "lack the ability to fully realize what their choices entail".