What are the symptoms of being underweight?

Underweight: Body Mass Index (BMI) of less than 20 is considered Underweight. Anorexia is an Eating Disorder with underweight. People who are underweight may have increased risk of Anemia, Heart irregularities and Osteoporosis. People who are underweight can find it extremely difficult to put on weight. See Physician for Diagnosis, have all necessary Lab done; have treatment. See Psychiatrist for Therapy.