Where can I find some statistics on weight-loss? I'm looking for a
distribution table similar to what you would get when you look at
incomes. The ideal answer would have something like:

OF THE US POPULATION THAT HAS LOST MORE THAN 25 POUNDS IN THEIR LIFETIME:
Loss of 25 or less  40%
Loss of 25 - 40  20%
Loss of 41 - 60 20%
Loss of 61 - 80 10%
Loss of 81 - 100 5%
Loss of more than 100 pounds 5%
TOTAL 100%

The ideal answer would fill in this table (or some similar type of
distribution table) from a reputable source.

Over a lifetime, I would expect that most on-and-off dieters would
have lost (and usually regained) a total of more than 100 pounds. I
know I have. Before I managed to stabilize my weight, I probably lost
and regained the same ten pounds every six months.

That's a very good comment by PinkFreud and I did try to incorporate
that in my question but couldn't find the best way to word it. I guess
it would be
"greatest loss at any one time/attempt" - it couldn't be the total of
weight lost over a couple decades of "yo-yo" diet habits.

So, yes, to clarify, it would be for amount of weight lost at one
time, during one effort/diet period.

Have you checked with the National Weight Control Registry?