Loss of appetite can again be due to certain medications, drug abuse, depression, AIDS
, acute and chronic infections, cancers and hypothyroidism. Either you do
not eat well or there is increased metabolism as in hyperthyroid states, HIV, cancer etc. Poor absorption as in irritable bowel syndromes and malabsorption syndromes too is possible. Malabsorption syndromes are seen in intestinal tuberculosis, HIV, tropical sprue, parasites in stool and Whipple’s Disease.