Are you aware that changes in appetite (either a decrease or increase in appetite) can occur in behavioral disorders such as anxiety, depression, and eating disorders? They can cause an individual to lose the desire to eat or lead to overeating in order to cope with constant feelings of sadness and stress.
Effect of drugs
Do you know that drugs (cocaine, heroin, amphetamines) and alcohol can also lead to changes in appetite? Physical states are also not left out in the causes of a change in appetite.
These include pregnancy, heart failure, and other illnesses. It is important to seek professional help especially if the change in appetite has become associated with obvious loss of weight/excessive weight gain.