Girlfriend hardly eats. no appetite, nausea and food tastes bad. has fever. tried bananas, bread, easy foods, hard to stomach. body trembles. cause?

Many possible: There are many possible causes for this, including infections such as the flu or hepatitis, etc. When someone has the flu, they generally don't want to eat -- but it lasts only a few days. They usually will take fluids, which is important. If this has been going on for a week or more, her skin is yellow, or she is refusing fluids also, she needs medical attention.

More info needed: Does patient smoke? Has there been weight loss? Normal menstrual period? Any possibility of any non-prescription drug use? A careful and comprehensive examination with blood work is needed--especially sugar and thyroid testing. Best wishes!