I think I would stay away from celery. Those nasty strings are rough on your insides.
I have found that now that I am doing so well on Remicade I have gained a few pounds but my biggest problem is not being regular so I get bloated and gain that weight. I have been taking Milk of Magnesia once a week and the bloating and weight have dropped a bit. I have tried to add some fiber to my diet because I was eating baby fruits and vegetables which sit nicely and don't have many calories or additives.
It just is so tiring having to worry about going too much, not going enough, having to go when you aren't near a bathroom, being near a bathroom and not having to go, just missing a bathroom by a few seconds.... it just seems to have taken over my life.