I am a girl and under weight for my age (70 pounds at 13 years ) and i do gain weight, however not body fat. what should i do?

Time: At age 13, your female hormones are not yet fully active. When they do reach full potential, you will start to fill out and become curvy like a woman's physique. In the meantime eat a healthy diet with plenty of protein, fruits and vegetables and exercise regularly. You may be genetically programmed to be slender, in which case be grateful. Thanks for trusting HealthTap!