Let's use logic instead.
Yasu bought to him some sushi the day before and we have seen Zoro eat on a boat when he received the news about Luffy's defeat. He escaped for days from the samurai looking for him eating poisonous meat, resulting in him having just a tummy ache.
Zoro fought without any difficulties until Kamazo stabbed him and then he proceeded with defeating him.
After that his last words where "damn, i got injured before the final battle" and he fainted.
The day after that he was screaming for the wound on his shoulder. Therefore i ask you, how long would you continue with this starving thing before you accept it was just a (bad) plot device and that the starving excuse makes no sense?
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He just fainted for the wound because Oda needed that, there is no shame in that
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