Perhaps I will add this: If we left the word as just “foods”, that “no person shall advertise foods”. Then, the question is, “Which foods?” The way it's worded in the original clause, there's some vagueness to it. We don't know what “contribute” means. “Excess” would have a whole definition as well. “Excess”, depending on the way you look at it, can be an amount or a percentage. It changes for different groups. How do we say which foods would be included?
The way we would usually do that is that we would have something to point to—a regulation—to help define which foods those were.