It has been proven that fiber is effective in the treatment of multiple nosological entities, specially of the colonic pathology. In the present study, two dose of Glucomannan (3 gr/day and 4 gr/day) were evaluated within the modification of the intestinal habit and stool characteristics. 60 patients were included in a random, parallel, double blind, cross over trial study versus placebo. The modification of the intestinal habit was evaluated through variations of daily and weekly evacuations, appraising the stool's consistency and size, satiety after meals tiresomeness between meals, constipation, diarrhea and flatulence. An increase in the number of daily and weekly evacuations during the Glucomannan vs placebo treatment was appreciated and, between the two dose of Glucomannan, a difference was observed as to the large the dose, the large the number of daily and weekly evacuations. Evacuations during the phase of Glucomannan 3 gr/day increased 0.5 times per day, 3 more per week above baseline values. On the 4 gr/day treatment of Glucomannan evacuations increased 0.9 times per day, 6 more per week above baseline values. Patient during the placebo period presented no statistically significant different. No difference was appreciated as to post-meal satiety, nor tiresomeness between meals, possibly due to treatment periods being 5 weeks long. No larger number of cases with diarrhea or flatulence were appreciated with the use of Glucomannan. Glucomannan proved to be superior to placebo, and the 3 gr/day and 4 gr/day doses turned out to beneficial in the improvement of the assessed parameters--better results were obtained using 4 gr/day of Glucomannan than 3 gr/day.