(Please excuse this for being slightly off-topic, but the Paleofood
community are the best resource I know for this sort of thing.)

There is a fellow in the office I have just joined who is about 350lb [to
judge by the picture at
http://www.kaiserpermanente.org/medicine/permjournal/sum00pj/shadow.html ].

I would like to introduce him to paleo exercise and food, but do not want
to do so if making the change could have no beneficial effect on his
health.

My question is, can you point me to any evidence either way as to whether
any seriously overweight people are stuck with their obesity, no matter
what?

Keith