As a former fat kid who also had loose skin/had to fill out, the thing I would recommend the most is consistency in weight training.
To give you some examples on how I transitioned over 3 years of weight training as a natural (I did take a $h1t ton of stimulants/pre-workouts, only thing that kept me going sometimes.).
Me at 315+ lbs:http://sphotos.xx.fbcdn.net/hphotos-ash ... 3535_n.jpg
Me after cutting down to 220ish with only a couple months of weight training under my belt:http://i46.tinypic.com/bi12s2.jpg
Recent pictures of me:http://sphotos.xx.fbcdn.net/hphotos-ash ... 0922_n.jpghttp://sphotos.xx.fbcdn.net/hphotos-ash ... 8085_n.jpg
I post these just as kind of a motivator for you - that while it may seem like it takes awhile, and the changes will be subtle over time, if you consistently weight train (and train like you mean it) you will see a huge improvement in the long run.
Also, when you're in the gym - do whatever you have to, to stay motivated - if you have to look at yourself in the mirror because seeing the changes that have happened motivates you - then do it, fv(k anyone who thinks you're conceited, they have no idea where you came from and the work you had to put in to get there.