Have a diet which is high in protein( 60-80 gms per day) . Total calorie intake should be 2500-3000 calories. Natural Sources of protein are dal, sprouts, whole legumes, milk, curds, paneer, nuts, dryfuits such as almonds and walnuts. Non veg sources are eggs, chicken , fish .
Next Steps
Add 45 minutes of Exercise such as weight training to your daily routine - It will help to convert to protein to muscle mass.
Health Tips
Avoid Supplements till you have exhausted natural sources.