Bowel Malnutrition.

Ive been trying to find information on what can happen to the bowel and what symptoms you could expect if the bowel begins to suffer from malnourishment . I have been ill five years and after 3 years of very low food intake (maybe one fairly normal sized meal per day , im 29 male approx 6 foot)began having spasms as well as a fullness feeling and when checked at hospital they said that the bowel was heavily inflammed but all the tests came back neg so they labelled it IBS but im not convinced . I have had no bouts of diarreah (diarrhea) but have occasional constipation but even after a BM it still feels like i need to empty again.

Many thanks,

Jon