Loss of Appetite

When you're sick, you frequently lose the urge to do practically anything. Even essential biological functions like eating might be put on hold, even if you're not in the mood to physically move around and accomplish stuff. Appetite loss is a very common sign of many diseases.

Again, blame the cytokines for this one, since your body uses the suppression of appetite as a way to concentrate on healing. As much as 15% of the energy your body uses each day is consumed during digestion. When you don't eat, your body can use that energy to help you fight the illness you're dealing with.

The other reason is that it's quite obvious you don't need or want to be putting extra food inside of yourself at that time if you're vomiting because you have a stomach infection and are feeling under the weather. Therefore, until you are able to eat, your body is postponing the want to do so.