Mainly the cognitive problems. I just get too swayed by online testimonials for my own good. And I have a friend with diabetes who is doing better with low carb. Of course I don't have diabetes... But Dr Myhill's website says CFS people are prone to metabolic syndrome (precurser to diabetes) so I am trying to forestall that.
Im on a low carb diet with my ME/CFS due to metabolic syndrome and prediabetes (hyperinsulinemia). As you have read metabolic syndrome is supposed to be common in ME/CFS (and most drs will miss this). Some with ME/CFS go onto low carb diets due to issues with candida and in their cases can suffer from candida die off which can make them sicker at first. If you dont have either of those issues and its not helping, forget it and look at other diets as you are doing.
(be aware that if someone is doing a very low carb diet ones body will be getting its energy instead from fats so these are needed in diet)
As to "which diet".. there is no diet really best as each of us is quite individual in our dietary issues if we have them with our ME/CFS (extremely common to have some form of dietary issue with this, it can take a very long time to sometimes figure this out). You may want to look at the idea of that you "could" have some food intollerances to figure out, seeing these are common in ME/CFS.
My food intollerences or issues with certain foods with this illness have been
- dairy (which can give me headaches but I seem to be fine with that now),
- sulfar foods eg too much of foods such as brocolli, eggs etc give me issues (I had my observation that some of those foods were making me ill further confirmed to me by finding out I had a certain genotype which often has this issue)
- peanuts/cashews
- mustard
- artificial sweeteners
- a food colouring they use to make some foods green
- coffee (caffeine)
- gluten
I havent had any food intollerence testing done so I have no doubt if I did I would find out I have more issues as it took me about 3-4 years just with observation my body with dietary changes or getting clear symptoms to foods to figure out what I had issues with on top of my issue with carbs.
Intollerances to fructose, dairy, artifical sweeteners, coffee (while that helps others) and gluten are all common in ME/CFS. It can be tricky to figure out as reactions may not happen till you have a certain amount or things in combo and different things may flare up different symptoms.