system
Given the following post, respond as if you're commenting on Reddit:
human
I've heard people describe how they became sick when they ate meat after a long time being a vegetarian. Does one's digestive system actually change from eating a vegetarian diet, and can then eating meat actually make one ill? Or is it more of a psychosomatic response to eating meat?

I'm curious as I would assume that the body wouldn't reject a kind of food that it had adapted to consuming simply because it wasn't "used to" it anymore.
gpt
This occurs due to our bodies changing bacterial flora. our digestuve tract is filled with bacteria which are help to digest and breakdown food. When we change it diets for a long enough time the bacteria composition in our guts also changes. Thus when they would go back to eating meat it would cause digestive discomfort due to the lack of bacteria to assist in digesting meat.
However, there is also a good chance that some of the discomfort might be psychological.