Oh?
Food sizes were built into the game later (ie: not at launch?)
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edit: just searched through the patch message site and didnt see anything useful about putting in food sizes.
Link:
http://www.tski.co.jp/cgi-bin/namazu...mal&sort=score
I did see one, from 2001 (velious) that mentions that forcefeeding food causes it to last half as long -
http://www.tski.co.jp/baldio/patch/20010417b.html - so it was in place during that time at least.