The several hours of fasting that is done prior to a liver/gallbladder flush is highly recommended making it more likely that you will be able to keep the olive oil mixture down...I believe that others have used sips of juice to offset any blood Sugar problems during the time it takes to do the flush. You might want to post this question on the Liver Flush Forum and ask about hypoglycemic reactions during the flush.
If you are interested in doing any more prolonged fasting...you might want to locate a health practitioner that carries Metagenics products and give UltraClear Plus a try. It is a powdered medical food used specifically for detoxification and contains proteins....as well as a multitude of nutrients...that assist the detox process.
Wolcott's book is fantastic...but unfortunately it doesn't address fasting, cleansing, detoxification and the like.