Any illness can reduce or eliminate your appetite. But if the illness is treatable, appetite should return after treatment, says MedlinePlus.
MedlinePlus mentions potential causes of appetite loss:
- Emotions such as sadness, depression or grief.
- Serious illnesses such as cancer or HIV.
- Use of certain medications or street drugs.
Contact a doctor if you are losing a lot of weight without trying, or if decreased appetite occurs along with other symptoms.