chatgpt says up to 72 hours of fasting for the colon to be fully empty or it laxatives can be used to manually empty it fully after 12-24 hours and to know when its successful is when "Once your stool output is watery/clear, you're done"
so fast for 24 hours (for the food to be processed), then take laxatives to clear all the shit in the colon; thats how you fast for the shortest amount of time while also ensuring no shit is kept that could slip out when CTB
@Jadeith @astroproto