S O F I S T I K said:
Well, I don't want to get like real big, I just want to have good definition, without looking skinny, lol.
^meaning you have to put on muscle.Yes some people have a problem with putting on weight because of their metabolism.And to put on muscle you have to eat alot.Food is inefficient if you want to do it in a healthy way.I don't think you want to eat 20 pounds of chicken a day.
What you need is weight gainer shakes.It's a high calorie shake,but it's healthy.It contains the right proteins,carbs,vitamins,amino acids to get you going.Go to a health food store and pickup one of these.
Weight training won't do you anything if you don't eat enough.As a matter a fact,weight training and not eating enough will put your body in muscle wasting mode.What this means is,when you finish working out,instead of your body repairing your muscles,it will just break them down because it lacks the neccessary nutrition to carry out protein synthesis.
Since you have a fast metabolism,you need to eat 18 x your bodyweight(lbs) in calories if you want to pack on some lean muscle mass.So 18 x 140 = roughly 2500 calories.It is essential you get at least this many calories.
I wouldn't worry about getting real big lol,you can stop the muscle gaining process whenever you think you have enough,then go on to maintain.