22.
I am 5'9 and 135 pounds (give or take a pound).
I have no idea where the weight would go, as I can't get any.
Well, I felt better when I was active. My activities were lots and lots and LOTS of rock climbing (bouldering and sport). I stopped that to lose some upper body mass, and it worked really well. Like I said, I lost 15 pounds in muscle, most of which was probably upper body. I have a little extra skin on my upper arms from where the muscle was. It's nice in a weird way. I was also running, I was up to 5 miles, 3 times a week, but it went down to 3 miles, then to 2 miles, and now nothing. I kinda got lazy.
I've been meaning to get back to running, and doing some cardio exercise, but that's on hold right now while I figure out the gym situation at school.