Both anxiety and depression can cause an individual to lose his or her desire to consume food. Conversely, both can cause patients to engage in overeating in order to cope with constant feelings of sadness and stress.
In addition to anxiety and depression, there are a host of other health issues, both behavioral and physical, that could be contributing to a change in appetite. For this reason, it is important to seek professional treatment in order to explore what might be causing a loss of or increase in appetite.
For more information on loss or increase of appetite, visit the National Institute of Mental Health.