User blog comment:Xilinoc/Realistic One Piece/@comment-24769684-20150525202904/@comment-2125188-20150527181737

Zoro was only starved for about 9 days. It can take up to 2 weeks for an entire a human body to shutdown. In the case of Zoro it would take almost the full 2 weeks, cause once your body starts to run out of resources, it then takes energy from your muscles (since Zoro has a fair bit of muscle it would take longer for the body to use up all it's energy), it then takes energy from your vital organs until your body completely shuts down.

However in saying all that, Zoro would not of had the energy to free himself or fight when Luffy tried to free him. Luffy and Zoro still would've defeated Morgan, but would've ended up a fair bit more wounded.