Nausea
Nausea is a status condition that prevents characters from eating food until it wears off. It sometimes occurs when susceptible species eat a contaminated chunk of meat.
Nauseated characters may only consume food if they are at, or near, starving, but doing so is penalized. Permafood only provides 50% of their normal nutrition, and chunks restore even less (15% - 35%). On top of this, eating any sort of food has a chance of inflicting sickness.
There is something wrong with this meat. (Onset of nausea)
You can't stomach food right now! (Trying to eat while nauseous but not starving)
Your stomach is not as upset anymore, and you want to eat. (Nausea ends)
You force it down, but cannot stomach much of it. (Eating food while nauseous)
That was not very filling. (Eating a chunk while nauseous)
That was extremely unsatisfying. (Eating a chunk while nauseous)
You feel ill. (Onset of sickness)
History
Nause will be removed in 0.12.
Nausea was introduced in 0.10. Prior to that, contaminated meat simply directly caused sickness 1/3 of the time, leading to much tedium where the player would then simply eat many more brown chunks to become satiated, and then usually wait out the sickness, as not regenerating health during a fight can be quite dangerous.