Purpose: An ideal cleansing regime to prepare a clean colon is important for yielding best results during colonoscopy. Many centers practice strict dietary modifications - ie, skipping more than one solid meal 1 or 2 days before the procedure with the consumption of a bowel cleansing agent. No formal studies have been performed to determine how long a patient should withhold solid meals during bowel preparation prior to an outpatient colonoscopy. Materials and methods: A randomized prospective controlled trial was carried out with patients who underwent elective colonoscopy at a tertiary general hospital in Malaysia for 7 months' duration. Patients were randomized into one of two groups. Group A patients abstained from a solid diet for 24 hours (the last solid meal was breakfast the day before the colonoscopy). Group B patients abstained from a solid diet 14 hours prior to the colonoscopy (the last solid meal was dinner the day before the colonoscopy). We standardized the time for the oral intake of sodium phosphosoda in both groups. The Boston Bowel Preparation Scale was used to grade the cleanliness between the two groups and a score > 2 was taken as clean bowel preparation. Results: A total of 178 patients (each arm had 89 patients) were recruited for this study. Group A showed a mean bowel cleanliness score of 3. Group B showed a mean bowel cleanliness score of 2.5. However, there was a significant difference in bowel cleanliness between the groups (P <= 0.05). Conclusion: Abstinence of solid food for either 24 hours or 14 hours prior to the colonoscopy both produced clean bowel preparation scores. Patients who can afford to skip more meals should stop solid food intake at 24 hours prior to colonoscopy. However, for patients who are not able to fast for long, they should be allowed to take solid food up to 14 hours prior to the procedure, thus reducing the need to over-starve them.