I would say no, because I know I could be so much fitter than I am, but I'm lazy and haven't got off my arse that much this year. Last year I was on the bike a lot and therefore was pretty fit, I weighed about 70kg (I'm pretty much 6') and did a lot of long rides as well as hill walking but this year I haven't been out on the bike as much (though I do enjoy it a lot when I do) and the little swimming/walking/climbing I fit in is not much compensation!!
Having said that, though, on the flipside of this, I can 'push myself' to a greater degree than most of my friends, I seem to be able to block out the pain and carry on. I don't know if this is a good thing or a bad thing, really, as it does mean I get more injuries, feel horrible afterwards, etc.