After that day till they entered that story, Fatty spent most of his time sitting in meditation, and he even stopped eating any meat or fish. That was his effort at the very last moment in order to get in the best condition before the story started.
Fatty himself said that he sometimes really regretted of having exchanged for this Taoist physique. There were not many prohibitions, but according to his experience, when he was feeling unwell after having too much meat or fish or drink, the effect of his spells would be reduced by a few percentage, and such reduction would cost his life in a story world.
Therefore, these days Fatty could only watch Su Bai and Ego dine on various take-out dishes while he could only drink rice gruel with pickles. And he had to stop before he was full, which tortured him a lot. However, he could temporarily hold back his desire for food in order to survive.