I was 175 when I was like 17... I think it was just a matter of stuffing my face whenever I had the opportunity. I worked out a lot, and managed to stay in decent shape. When I left the house, I lost a LOT of weight (I've been down to 138, but definitely NOT healthy)... now I only eat once a day, and its usually something like PB&J or ramen... I need a better job.

Just eat lots of carbs and be sure to excercise to make sure it doesn't just turn to flab.