On the day before (day 1) your colonoscopy, stop. This diet slows down your bowels and gives them a chance to rest. Fiber is the part of plants that your body. This diet slows down your bowels and gives them a chance to rest. Fiber is the part of plants that your body. Print this chart (pdf) for easy reference. See the clear liquid chart for the day before, and day of, your colonoscopy.