I do get the messages from the characters that say that they're hungry, but I'm not sure if there is any meter, or a way to tell I have fed the said characters well. Any help with that will be appreciated.

There is an invisible meter. You need to listen to what the characters say in order to know what hunger level they are at. The messages are usually pretty obvious.

This page explains it pretty well:
http://ultima.wikia.com/wiki/Food_Values_in_Ultima_VII

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In Ultima VII (both parts), eating is absolutely essential for keeping your party at full strength. However, each food item has a different feeding value. The feeding status of a party member is indicated on a 31 point scale, with 31 being full and 0 being starving to death.
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There is also a table on that page with the feeding values of each food item.

There is also a fork and spoon icon that will appear under the status page of the paperdoll to indicate hunger, which also appears prior to the character verbally complaining of hunger