If you say, "That was a filling meal" I don't think there's any ambiguity.
While it's true that "filling" as a noun has a different meaning also related to food, the fact that in one case we're talking about a noun and in the other case about an adjective means that it is rare that a sentence using the word would be ambiguous.
Well, I suppose if someone pointed at a piece of cake and said, "That was filling", it might be unclear if he was identifying the stuff inside the cake or commenting that the cake as a whole satisfied his hunger. But in real life there would almost surely be context to clarify which he meant. As people rarely point at food and say, "That is fruit" or "That is poultry" with no one asking what it is or some other lead in, if at a dinner someone pointed at a cake and said "That is filling", I would assume that he meant that it filled him up, and not that he felt it necessary to identify it. In practice there is rarely cause to identify something as filling, we're more likely to describe it. Like, "The filling was made with whipped cream" or "Sally spent hours preparing the filling for the muffins."
If the sentence is ambiguous without context, add a couple of words to clarify. As I say, aside from the simple sentence, "That is filling", I'm hard pressed to think of an ambiguous sentence. That one could easily be resolved by adding a word or two. "That is the filling" would clearly identify it as the noun. "That cake is filling" would make it an adjective.
Not to say there might not be other words to express the meaning, as others have suggested, but I think in practice there would rarely be ambiguity.