The fact is that I've always been a big boy, I was 245# as a freshman in HS, and 265 when I started playing football as a junior, and 290 around the time that I got into mountain biking in college (and wrecked my back badly enough that I was out of football). I'm also 6'4" with a very large frame even for that height and a lot of that weight is muscle...
Well, around 28 I got married, and by 35 I was sitting in my office realizing that EVERYONE that I worked with was overweight and they all were going to the doctor weekly with all sorts of problems. I'd ballooned up into the mid 300's (well over 325, which was where my scale went up to), and was starting to get all sorts of aches and pains and other things that I couldn't explain. I realized that I not only didn't want to die young but just as much didn't want to live and be unhealthy having to deal with medications and Dr's visits...
A friend/co-worker of mine lost 65lbs by stopping drinking sodas (we're IT guys, most of us had a dorm fridge under a desk somewhere full of sodas, we started our mornings with a soda and often had half a dozen by the end of the day), and I thought "hey, I can do that..." and ended up cutting sodas, slowly limiting sugar and simple carbs... and over the span of about 2-3 years, maybe a little more, I'd lost over 100lbs. At the lightest I was just under 240, I was actually lighter than I was as a freshman in HS, and nothing fit (honestly I have crazy proportions, nothing fits anyway, even in the mid 300# range I was only wearing size 38-40 pants, but my suit jacket size has always been in the mid/high 50's).
That was 12 years ago. Back then I told myself that I wouldn't let myself get back over 245#, but I kept getting more and more serious about the gym. I ended up getting very into powerlifting and decided "I'm going to monitor my body fat percentage and as long as it doesn't go up I can gain weight..." and I've stayed at the same bodyfat percentage (the more muscle you carry the easier that is, I recently learned that I regularly work out with 40lbs more than the state record for my age/weight class and I've found that as long as I limit sugars I almost have to force feed to maintain my bodyweight and grow muscle).
Currently, I hover around 270#, I know, some of you are thinking that's really big, but at that weight, I can wear size 33 pants and I hover around 18% body fat (not super lean, but considered "lean athletic" for my age). I have some powerlifting goals and a timeline set, and once I reach either I intend to cut back down to under 260, hopefully, at least for now, I'll maintain my lean body mass. Why 260? Well because no matter what your body fat percentage is your health outcomes are statistically better under 260 (though interestingly there is some evidence that as you get older too low a bodyfat percentage lowers life expectancy, somewhere in the 20-22% range is optimum).
College3.0, you mention not having the support of family... I'll tell you that for me that family was actually the hardest part of this. Having family that doesn't get what you're doing or why you're doing it was probably the hardest thing, almost like someone actively working to make you fail every step of the way. OTOH, during this process, I've 'acquired' ;-) 7y/o twins, which although not my original reason for doing it, end up being pretty good motivation for staying in shape.