if you weigh only 109 lbs at your height, chances are that its your metabolism keeping you weight down and whatever you cram down your throat wont help you gain weight... it'll just be hard on your arteries. what you should do is workout for 1 hour in the weight room 3x a week, doing low rep high set workouts. this will help you become a lot hungrier, and you will just add on a lot of mass to your frame that way. i used to be 6 ft 3 and 160 lbs, now im 6 ft 3 and 235 lbs, so i know this method works really well.