I've recently turned 40 and on my birthday, I weighed 278 lbs at 6'3". I've usually hovered in the 230 lb range during my adult life, but really feel best when I'm around 200. For a while, I tried running but my knees didn't hold out for long and I could never get quick enough to be happy. This spring, I decided to start biking so I brought my old MTB to the LBS and got some issues sorted out. I also purchased a 2001 Trek 2000SL from a coworker for not too much money. I really didn't take my first ride until June 7th, but 22 days into riding, I've ridden 250 miles and I'm picking up the pace. I have a 16 mile commute to work and intend on riding to work every day next week after doing it three times this week. I'm now down to 260 lbs and hope to be sub 240 lbs by the end of summer. Well, I hope to be even lighter, but I'm being realistic. My commute to work has about 7 miles of paved path, 4 miles of gravel path, and 5 miles of mixed road/sidewalk travel. Because of the crushed limestone/gravel portions of the travel, I've been riding my MTB because I don't know if the Treks 25mm tires are up to the task. The going is slow, but I'm getting marginally quicker. I've gained 1.5mph from the first time out on the MTB bike. It's amazing that about 3 weeks ago, an 8 mile ride was quite tiring but now at 16 miles, I'm not even winded.