The effects of dietary fibre on upper and lower gastro-intestinal transit times and faecal bulking.

A total of 10 obese patients (body mass index greater than 25) undergoing treatment with a very low-calorie (330 kcal/day) liquid diet were treated without and with 10.5 or 21 g/day dietary fibre. Mean (+/- SE) faecal bulking increased significantly (P less than 0.001) in a dose-dependent manner from 314.8 +/- 54.4 g on a fibre-free diet to 517.2 +/- 45.4 g and 748.9 +/- 78.5 g, respectively, over 5 days on diets containing 10.5 and 21 g/day dietary fibre. Total mean colonic transit time decreased from 53.9 +/- 3.6 h on a fibre-free diet to 25.8 +/- 44 and 17.3 +/- 4.6 h, respectively, on diets including 10.5 and 21 g/day dietary fibre. Both right and left colonic transit times were similarly affected but no effect on orocaecal transit time was detected.