I've been battling CFS for almost 27 years, and am convinced the root of the problem is a gut pathogen. My problems all started when I was taking broad-spectrum antibiotics for acne, leading to intestinal candidiasis, which I was able to overcome thanks to the Yeast Connection by William Crook. Although candidiasis is no longer a problem for me, I am still tired and brain-fogged after every meal I eat. (I feel relatively normal until I eat something (anything at all), and then I start to feel progressively more lethargic, brain-fogged, and tired. The symptoms peak a few hours after my meal and then begin to recede).
And if I eat and then go to sleep, I feel AWFUL when I wake up, especially if I eat hard-to-digest foods (such as foods high in fiber). What clearly appears to be happening is that some kind of organism in my gut is feasting on the undigested food particles and releasing toxins in the process. If I'm awake while digesting my food, this still happens, but to a much lesser degree.
I suspect the pathogen is either an enterovirus (like Dr Chia suggests) or some kind of bacteria.
Drew