I am 21 years old but i will not look like that everyone is asking me that in which you are studying. i want to increase by weight and body size.help?

Dress wise/hit gym: Go to a gym and find a personal trainer that can help achieve your goal safe. Eat healthier so you can build muscle. Slow and safe is the way to do it.

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. Proteins: egg white, chicken breast, salmon, ... Better fats: olive oil, peanuts, almonds, tofu, ....