I am under wait what should i do to put on wait?

Protein: If you do not have any kidney problems, try eating lots of protein, like meat, chicken, fish, eggs, yogurt, cheese, tofu. These should help build muscle without adding fat. Also, exercise regularly, including lifting light weights.

UNDERWEIGHT: Perhaps you have no appetite or picky eater. Take more calories by eating high calorie foods like cakes, icecream, rich looking pastry, or any kind of food by increasing the amount intake.