I am 19 years old boy. My height is 5.5, weight is 46 kg. I know I'm underweight. I've been taking exercise for approx. 2 years. I've achieved toned body but unable to gain muscles. What should I do to gain weight speedily?
This is too vague to give a specific answer to your needs but the easiest way for an underweight person is this:
Eat every 2 hours. You need to jam a lot of calories into your diet and eat often since your metabolism is so quick.
Eat an additional 500 calories a day
Eat 150 grams of protein, and 200 carbs a day(for your current bodyweight)
Workout 3 days a week, this is best for a beginner. Use rep schemes anywhere between 5 and 10 reps
Do more heavy compound exercises like deadlift, bench press, squats, etc.
The trick to gaining muscle is really 80% diet.. you'll be very full and wanting to throw up during the first week because it'll feel like your binge eating.