Damn I wish I could get away with that Matt!
I'm really lucky, I don't eat big meals and never have done. I almost trickle feed throughout the day which according to my doctor has meant that my metabolism is really high. If I'm ill and don't eat for a day or two you can see a difference, because my body is basically always looking for stuff to digest.
I went on a diet a few months ago to try and put weight on, because I actually don't like being a rake. I used an app (my fitness pal or something) which recorded the calories, vitamins, protein etc which I have per day. For 6 months I ate pretty healthily, 3000cal per day lots of protein etc and all decent stuff. My weight didn't change at all. I did notice other benefits, no afternoon slump, sleeping better, but my weight itself stayed pretty much the same.
That is interesting! I guess it's better to be on that side of it but that still must be a struggle. At least you get to eat whatever you want! I had a friend years ago who was the same, he was really tall too think his BMI was about 16.