I think it's best to do light exercise and not strenuous exercise that raises the body temperature a lot, because this will make inflammation worse and tires you too much Qigong is ideal for me as well as walking. Swimming is good too of course, but don't exert too much... For diet there are a lot of approaches but I never tried fasting on liquids except the odd day or two and I think some meat as long as it's not red meat is good to repair damage and aid recovery. I stick to free range or organic chicken mostly. Whey protein isolate is also good and especially the hydrolysed form. I think fasting will definately make some people a lot weaker if they are already weak and maybe anaemic and have lost a lot of minerals.
So my approach is to be strict with diet and make sure I get all the mineral and vitamins I need in the right quantities and then be patient for improvement to take place cause it can take time to stop a flare. Supplement forms are important for maximum absorbtion. especially magnesium and iron.. The bisglycinate kind always worked best for me and I still use them even though I've been in long remission and I always maintain a good diet. A lot of things help but don't work on their own. Good probiotics in the right dose help. You have to keep on eating a good diet even in remission or it probably won't last but it doesn't have to be so strict as when in a flare.
Taking drugs like immunosuppressants antibiotics and steroids comnplicates things a lot though. I've taken none of those in the last 7 years