Perhaps I could fill it in a bit. Are we talking about “prescribed foods that contain more than the prescribed level of sugar”? It said “prescribed” twice—“prescribed foods that contain more than the prescribed level”. Or, are we talking about foods that contain more than the prescribed level of sugars?
In the latter you don't need to have the “prescribed foods”. You're just going to be setting levels—no food that contains more than “blank” amount of sodium, or whatever, shall be advertised for children. In this case the “prescribed” is said twice. You have a list of foods and the amount of prescribed....
Again, I want to know what's in your mind when we say what kinds of foods will be prescribed. It's not just the constituents; it's both.