Fiber is not a good food for humans. Breastfed infants get no fiber and their bowels work fine. Most people in the world have low fiber diets and don't have health problems like we do in the U.S. The longest lived people, as in Sardinia and Okinawa, have very low fiber diets.
I've been following Mercola's diet advice and somewhat a Paleo diet which he supports. But I just found the GutSense site and am switching to low fiber as well as low carb. Fiber by the way is mostly in carbs anyway. A laxative without side effects is said to be high-dose Vitamin C. So it's important to take that while transitioning to low fiber diet. Also the author says it's important to take L-Glutamine to restore mucosa in the gut lining and probiotics in capsules to restore microflora. He sells nutrition products for this purpose that seem to be very high quality and modest price.