From what I understand a lack of cholesterol can cause gallstones. Eating eggs should help and you can even take bile salts directly to help.
I cannot imagine some intermittent fasting, omad, or 48, or 72 hour fasts would be bad as long as you stay hydrated and have electrolytes.
I’m curious, what did you find that said fasting could make gallstones worse?
I would also recommend avoiding seed oils anywhere you can and increase saturated fats, drinking heavy cream is the best, the fats are surrounded by good stuff and it has no sugar in it.
Just my thoughts from research I’ve done.
Can you share what disease? I have a pretty awful illness that puts me in the hospital a lot but it’s still undiagnosed.