bachian saidI would love to be where you are at 19. I was already 6'2" and my weight was 130lbs. I agree with the recommendations of the poster above but I wouldn't count on your body helping you. When I was 24, already years past my puberty, my weight was just 140lbs. Puberty never gave me muscles. When nature forsakes you, you are the one in charge of acquiring what it didn't give to you, naturally or not. Your height is a blessing, you would be in far worse situation if you were taller.
I was told, "you are lucky", but never felt that way internally, being tall and under weight bean pole has the same dysmorphic feelings as someone short and fat. I mean, those of us natural ectomorphs are always accused of having anorexia or bulimia, which is far from truth, these are eating disorders, not thyroid, pituitary or growth hormone deficiency, we all cant be perfect mesomorphs, wishing, wont make it so
I am sure this has been discussed at length somewhere within RJ threads
Your Body Type - Ectomorph, Mesomorph or Endomorph?
Body type influences how you respond to diet and training. Understand your body type in order to plan your muscle building training and diet program.http://www.muscleandstrength.com/articles/body-types-ectomorph-mesomorph-endomorph.html
After reading the body type article in that magazine I started to understand more about how my body type worked, my metabolism, and gaining weight. Being an ectomorph I need to focus on calorie intake, long rest periods, and minimum cardio. It was only then I started making some real gains and I’ve never looked back.