Eating food in different forms - how hungry am i after this

Bit of an odd question - the Magi are travelling and cannot, for one reason or another, pick up additional supplies and need to ensure that the supplies they have last longer than they would otherwise.

If one of them were to turn their grogs into animals that would eat less than a human, say a mouse, whilst they ate their fill, would those people still be as satisfied with the food they consumed as a Mouse when the transformation ended and they became human again, or would they become hungry again?

I am pretty sure they would be satisfied with the food they had as a mouse.

Alexander of Jerbiton, in Magi of Hermes (he's the first one in the book) turns his covenfolk into tiny creatures to ration water when out in the desert.

Agreed - they would feel full.
You could also change the grogs bodies so they can get sustenance from odd things like soil. They might not like eating dirt but it makes food abundant, and an illusion could make it taste better too.

TMK they would still feel full.

For an argument, reverse the question. If you turn a camel, which had just drunk the water lasting it for the next days, into a mouse: would it burst and die, because a mouse could never contain that much water?

Keep you saga rules simple and focused, and don't waste time to discuss the digestion of animals in Mythic Europe, unless you absolutely have to!