I recently unicycled 300 miles across Africa. Photos here: http://www.matthewwegner.com/africa-unicycle-photos/
This was a vehicle-supported tour organized by Escape Adventures, who are absolutely awesome. They usually do bike tours; this was their first unicycle tour. I'd highly recommend them for any foreign tours: http://escapeadventures.co.nz/
I didn't lose any weight from training, probably because I didn't train enough.
But I think I discovered a lot of role models on the trip (I'm only 21). Surprisingly, this is only the second group of people where I've felt like I've fit in really well. A few people adopted me as a sort of surrogate daughter, and I've become really good friends with them.
Most of the people were quite well to do--we had a lot of retired engineers, doctors, and a real estate lawyer. We had a couple crazy wealthy people, but they behaved like anyone else. On the whole, they were very gracious people, very kind, and generally good-natured. Some of them acted like they were 60 or 70 or whatever, and some of them could have fit in at a frat party if they looked younger.
I didn't really have time to go off on my own much. I really sucked for the first four or five weeks, and I barely came to the next motel in time for a shower and the overview of the next day's route. Also, they usually put us up in motels located in strip malls, so we were often a couple miles away from downtown. Even if I'd been inclined to get back onto my bike, urban riding is still something I don't want to do if I don't have to. Even if you're a strong rider who's able to fit in side trips and still get back in time, the sightseeing opportunities are limited.
(But given the nature of this site, I wish I could post something really intellectual or otherwise related to hacking instead.)
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Addenda:
very frequently asked questions: What was the mileage per day? About 80 miles. The shortest day was 38 miles, the longest was 120.
What was the group size? About 50. The average age was 58, which surprised me. I expected to see a bunch of retired people, but I was the only recent college grad. The youngest person was a girl who had just graduated from high school; the oldest was an 80 year old man.
What was your fitness level prior to the ride? I ran at the gym for maybe 10 minutes, perhaps every other week. I was not especially fit, had never done any sports and was generally unathletic. Imagine my surprise when the tour booklet came two and a half months before I was to leave, recommending a year of training prior to the ride. =( Anyway, I put in about 1000 miles of training in those two and a half months. I was so afraid they would kick me out for being unfit that I didn't even dare ask them if they had that policy, lest it be true. It was pretty dumb of me to worry, in retrospect, since they'll just pick you up in a van if you can't make it to the next checkpoint, but I wanted the trip so badly that I avoided the thought of failure as much as possible.
How fast did you ride? The strongest riders probably averaged 20 mph. I think the 80 year old man averaged 12-13 mph in the hilly places like Oregon. He was terribly slow at going up hills, but the descents made up for it a bit. I started out averaging 11-12 mph, but with lots of help and mentoring I moved up to 14-16, depending on the terrain and wind.