What happens physiologically to people that causes them to lose their appetites when they are sick?
In: Biology
Eating takes a lot of energy and, in the natural environment our responses are adapted to, is often the way you get sick in the first place. So low appetite is one part of a broad behavioral change seen in sick animals called [sickness behavior](https://en.wikipedia.org/wiki/Sickness_behavior), which also includes reduced grooming (probably to keep others away because one might be contagious) and more sleep (which conserves energy).
The direct cause of all this are molecules called cytokines that are released during infection or other inflammation in the body. Those cytokines act directly on the part of the brain that controls appetite and other urges.
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