I am underweight, i am 27 years old, my height is 5 inches but i am underweight, inspite of whatever i eat i donot gain weight, please help?

See Dr.to find cause: Several things can cause this. The main ones are inadequate intake of calories, need for hydrochloric acid and/or digestive enzymes, malabsorption, inflammation of the intestines (possibly from intestinal parasites), celiac disease and other food allergies, vitamin/mineral/amino acid deficiencies and hyperthyroidism. A good GI doc or holistic/integrative doc can help you find what the problem is.