In reply to neil the weak:
Dave MacLeod did a talk at Stowmarket a few months ago, and one of things I remember ('cos I thought it rather funny) was the comments he made about his weight.
He was doing his Echo Wall project, and to start it he needed to shift lots of snow from the top. He showed us two photos, and his comments went something like this :
"This is 10 stone Dave, he can shift this amount of snow in 6 days, but can't climb for toffee"
"This is 9 and a half stone Dave, he can climb at the level needed for Echo Wall, but is really grumpy when he wakes up, you really don't want to be near him before he's had breakfast!"
Even at 9½ stone he looked thin, but still healthy (definitely not emanciated), and it was obvious that 9½ wasn't his natural weight, was only necessary for the project he was doing, and also that losing any more weight wouldn't have been worth doing.
And it was a trade-off between feeling grumpy and horrible and climbing at your peak, or looking better and feeling happier and climbing at a bit less than your peak. I'll take the second one.
Of course 10 stone Dave can probably still climb an E9 or something...