I'm 28 years old female weigh 39 kg. & i don't have any health issues except underweight. please just me pure vegetarian diet to gain necessary weight?

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 weight-training to increase muscle. Choices for proteins and some fats include tofu, olive oil, beans, peanut butter, hummus, avocado, ...