I often wondered, if the positive benefit of fasting is due rising cortisol levels. Fasting is a huge stressor for the body and in order to break down the energy storages, the body releases cortisol. But cortisol also suppresses inflammation and immune cells. Further if you withhold the body of arachnic acid (from meat, eggs, cheese, milk etc.), it can't produce certain pro inflammatory cytokines. In RA a short period of fasting (2 to 3 days) seems to ease symptoms. As well as to stop eating meat and eggs.
The arachidonic acid (arachidonate) issue is something I have been working on for 21 years now. I have posted on this oodles of times, including recently (somewhere). Simple restriction may not be enough, and may not be really desirable. We often have both excessive use of arachidonic acid and a deficiency, and its an essential substrate. The real issue is we are probably making the wrong eicosanoids, its not just about excess production.
We do seem to have excess stimulation of cyclooxygenase, which acts on free arachidonic acid. Arachidonic acid is also released when we drink alcohol, and I consider release of arachidonic acid may be our main issue with alcohol, not the other hypotheses I have heard. However we also have desaturase suppression, probably mostly due to decreased glutathione. Most of us probably need
more arachidonic acid, and to
use it less.
If I recall correctly, cortisol suppresses release of arachidonic acid but I am so rusty in this area now what I am not sure. NSAIDs suppress the enzymes, usually some part of cyclooxygenase. Fish oil (EPA, not DHA) suppresses arachidonic acid utilization via competitive inhibition, since its also processed by cyclooxygenase.
Arachidonic acid and cortisol are part of what I meant by metabolic issues. But with gut issues I also include excessive absorption of lipopolysaccharide, which might be a big player in ME as its a superantigen and we often have too much in our blood.