Malnourishment can have serious health consequences including being at risk for contracting very common infections and inability to heal. People responds in different ways when exposed to the same level of stress. Some people can not eat while others can not stop eating. Having a low appetite for a short period of time (i.e., less than a week) will probably not cause any problems as your body has a substantial reserve of essential elements. However, not taking in adequate amount of calories, protein, fat, essential vitamin and trace elements can all lead to poor immunity. In order to properly fend off pathogens and heal injuries, your body needs much more energy than you normally would take it on a daily basis. To go beyond these symptoms, it is very important to figure out potential problems in getting well. Mental and emotional stress can often be enough to lower one's appetite. But, if this continues for longer than a week, it is important to seek out a medical professional to find ways to ameliorate it. Sometimes, it can also be something physiologic like cancers. In the later stages of most cancers, patients may have very little appetite and can struggle to get adequate nutrition. It is important to figure out potential problems early on so I suggest your mother to schedule a visit with a primary care doctor
to receive a proper evaluation.