Sure, there is some adaptations.
1) Small amounts of unprocessed grains do not cause negative reaction in most people. However, processed grains, aka bread and pastas have an immediate and profound impact on the appetite because of the components added to it in the last 100 years (a far cry from 100,000 years ago). We are absolutely not adapted to deal with that.
2) Consuming unprocessed starch from grains and/or tubers leads to fast and significant weight gain when it is combined with fat
3) Grains contribute little to the palate and nutritional profile.
--> If you are trying to gain weight, consuming unprocessed grains is your choice. If that's not the case, dropping grains is a single easiest thing to do to control the weight and reduce it to the average weight range.