You seem to think that people that are not completely satiated are automatically cranky. That doesn't match my observation.
Also you may have multiple dishes. For example we mostly start with a collaboratively prepared soup - which thereby will be the right size by construction. Later we have some snacks or sweets or fruits. First the fresh ones, later if needed packaged ones.
I don't think I need that for my argument to work. My claim is that if people get, say, less than 70% of a meal's worth of food, an appreciable fraction (say at least 30%) will get cranky.
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