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Well, there is a wonderfully "interesting"
product in the USA called Cheese Whiz. It even has its own entry in Wikipedia.
For some reason many people seem to like it --- but I've always thought it tasted pretty awful.
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Your expression sounds to me like it means "not interesting or exciting anymore" or possibly "not energetic anymore".
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What context did you hear/read it in? Maybe someone just wanted to say that some cheese had gone bad.
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