I am very skinny n wld need help with a prescription that can be found in the uk and very active with no side effect that can make me add weight fast?

See Dr., then eat...: Don't think there is a weight-gaining pill. 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. Proteins: egg white, chicken breast, salmon, ... Better fats: olive oil, peanuts, almonds, tofu, ...