Turned 39 in 2008. Wasn't in bad shape, but didnt exercise regularly. Realized "40" was a year away, time to take better care of the chassis, so to speak. Started working with a personal trainer and running - 195 lbs, just a touch under 5'11.
Now (May 09) I've dropped 30 lbs to 165, and have never felt better. Decided two months ago to do a tri, and started a 10 week training plan.