Helping a friend after a colonectomy

I have a friend, very traditional medical model, who will have his colon completely removed on Tuesday. When I met him almost 3 years ago, all he thought about was his cancer returning (prostate and colon) and dying. I distracted him with dancing, but didn't impact him too much with alternative health information. Anyway, his colon will be completely removed on Tuesday. He only weighs 140 pounds and what I am hearing is he will now only be able to eat crappy food (white bread, etc., no fruits and vegetables. I'm concerned about nutrition and his survival. He plans on doing whatever the hospital tells him to. I would like to help him survive and thrive rather than eat less well. Can someone with experience help me know how to help him?

thanks