I'm also a fatty mate, and had quite the same "revelatory" moment when I was at my biggest: I walked out into the back garden and the neighbours' kid was playing with some friends. From atop their slide they could see me over the fence, and one of the friends exclaimed "Wow! That is a FAT man!"
I've never felt so humiliated, to be honest.
Right then, I decided to do something about it. I haven't stressed myself or given up junk entirely, but I took to exercising and have dropped around 2 stone in a couple of years. I know, a couple of years is a long time to do that, but that's been on and off the wagon.
At the start of the year my wife joined Slimming World. That, coupled with her regularly gym/swimming pool visits has allowed her to drop about 4 stone since this January. I stick roughly to the eating plan (though I'm a bit too much of a lush when it comes to the booze - my only major stick in the spokes) but haven't been exercising as much due to shinsplints and a few gout attacks.
I will say, though, that running a mile a day on the treadmill while I continued to drink, but ate on Slimming World principles, I dropped about 10lbs in four weeks.
Now that I haven't touched the treadmill or destroyed myself on EA Sports Active like I used to regularly, I find my weight yo-yoing week to week; 3lbs lost, 2 gained, 2 lost, 3 gained, 4 lost etc. etc. It's really trickling off...but exercise is the key.
You can't just sit on your butt eating diet pills and hope it's going to work. It isn't. You can eat PLENTY of delicious food and still lose weight. You just need to know what to eat.
If you want to talk about anything or want some more info from the wife etc., my email's in trust.