I'm 19, and I've always been 6'2", and 160 something, until last year. I tried using creatine for 3 months and really hit the gym seriously with a friend, and peaked at 182 lbs. Putting on about 20 lbs. of muscle in 3 months is impressive, but I lost almost all of it over the next year
. Back to 165 lbs., losing most of my muscle in my first semister at college. Not eating enough, not hitting the gym, and perhaps creatine had something to do with my getting skinny again. But the thing that really did it was the shitty food I've been eating at college. When you're hungry, don't eat a snicker's bar or poptarts. Go get a real meal. Sugar and carb loaded processed crap food does nothing for me other than surpress my hunger, which results in weight loss. When you're hungry, take the time to eat real food.