It will also be important to eat a low-fiber diet in the days leading up to a colonoscopy, a clear liquid diet the day before, and stop all liquids several hours before the appointment.

[15] All subjects were instructed to consume a low-fiber diet for 2 days prior to colonoscopy and were given the option of consuming a PEG-based preparation using one of the following dosing ...

But if you’re having a colonoscopy, this is when you’ll start changing your diet. The goal is to avoid too much fiber and eat “low residue” foods that clear from the colon quickly.