Hi folks --

As has been pointed out, there are plenty of vegetarians around who do seem
to be healthy and active -- well, maybe not "plenty," but I know some.

If I wanted to convert them to paleo eating, I would probably say something
like, "sure, you feel fine NOW; but by eating this way, you are increasing
your chance of getting cancer or diabetes or something similarly unpleasant
later in life."  We do have some statistics to back up that claim.