first off...whoever you talked to is an idiot. make sure you let him know that
secondly, there is no way of NOT being able to get big. some people have good genetics and some dont. for all you know you could be one of those people if you apply a good diet, exercise program and you stay motivated and you could prove the dumbas.s that gave you that advice out of his as.s wrong. i believe he was judging you by your CURRENT status. long, slim = most marathon runners or runners in general. it makes sense....but thats not advice to give regarding te FUTURE. anyone can get big, all it takes is time,dedication and the right diet plan, not to mention alot of other things but those are just a few. So tell that poster child for stereotypical big dumb guy to go lift some books and read.
that answer your question?