GAPS has been discussed here. Dr. Natash Campbell-McBride has a program for gut healing. Healing. It starts with meat broths and meat, cooked non-starchy vegetables, fermented veggie juice, whey from dripped yogurt - trying to remember what else. Stage two adds egg yolks.
As the gut heals, she introduces more and more foods. Eventually, the only things recommended against are the processed and sugary stuff we all know isn't good for us.
She says dietary fiber can cause inflammation in an already unhealthy gut, particularly in individuals prone to diarrhea.
I've been on the e-mail list for awhile and some of the stories of healing are very encouraging. She does say the ME/CFS is very complicated to heal and it can take some time.