What happens physiologically to people that causes them to lose their appetites when they are sick?
In: Biology
Congested sinuses lead to a sore throat (which means that you won’t want to eat, cause it hurts to swallow). It’s the snot travelling down the back of the throat that causes some of the pain – so when you think about it, having a belly full of snot can mean that you feel “full” even without eating anything.
Note also that getting sick often includes nasal congestion, and the nose is a critical part of the ability to taste. With less ability to taste, folks aren’t as eager to consume food.
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.
Think it thru. If you get sick (flu) you will loose your sense of smell and taste. How often during the day, do you feel not hungry but walk past something that makes your mouth water and immediately you start to feel a bit hungry and your mouth starts to drool? There can be other internal issues that cause nausea and although you might feel a bit hungry forgo eating knowing that it will make the nausea worse.
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