The first type is the person who digests everything they eat. They have no problem with any type of food and their digestive system is very efficient. This type of person is rare.
The second type is the person who has a sensitive digestive system. They need to be careful about what they eat and they may have problems with certain types of food. This type of person is more common.
The third type is the person who has a slow digestive system. They need to eat smaller meals more often and they may have trouble digesting certain types of food. This type of person is more common.
The fourth type is the person who has a very slow digestive system. They need to eat very small meals very often and they may have trouble digesting any type of food. This type of person is rare.