If we think about the way that our ancestors ate, they rarely ate high fiber foods in the amounts that we supposedly need. There is a reason that protein and fat transit the digestive system more slowly: they take longer to break down and become small enough molecules to cross into the bloodstream.

But without lots of grains to lead to inflammation in the gut, slower transit time doesn't need to be an issue.

For those who used to eat a lot of "healthy whole grains", suddenly having much smaller and less frequent stools can seem to be a problem. But it makes sense: those big bulky things were just filled with the byproducts of what we ate that our bodies could NOT digest. Letting the food we eat take its time through the digestive tract, and be actually absorbed along the way, is a GOOD result, not a bad one.