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According to your height you are underweight
at 55 kgs as the ideal is 65-80 kgs so you need to increase your weight.To increase weight it should be seen why you are underweight like whether you have any disease or any problem like hyperthyroid or it is due to stress
diet or genetic in your family.As it is normally the height increases in most males till 21-22 yrs and then they gain weight.Please consult a doctor and get investigated if required and treated if there is any problem.Please stay away from steroids
as if it helps in increasing weight it may lead to side effects like weakening of bones or metabolic problems.