In need of something thats going to assist me with gaining weight as im severely underweight ?

See Dr., then eat...: If one is truly underweight (based on height, family background, and body type), a Dr. can evaluate for a hormonal, digestive, or other disorder. If no medical cause is found, then one can add weight by eating more calories of nutritious foods, while also doing mild weight-training to increase muscle. Proteins: egg white, chicken breast, salmon... Better fats: olive oil, peanuts, almonds, tofu...