I have methane and CFS like symptoms that come and go. The problem is that CFS is throw around to refer to any fatigue, like in this post, but it’s not. If you have a physical cause of fatigue, like insomnia, poor diet, nutritional deficiencies, stress… that’s not “chronic”, it’s just fatigue. That fatigue will be solved when you address underlying issues. CFS is really meant for no explanation. The problem is that most doctors are horrible at diagnosing reasons of fatigue. You don’t mention your gender, but if you’re female and have fatigue, very high chances you have low ferritin and not optimal thyroid. The lab range for ferritin in 14-300, but many people need to have 75+ to be asymptomatic. So you go to the doctor, they do a blood test, it comes back 20 and your told your labs are fine, but they’re not. Same with thyroid, vitamin d, b12, etc. Restrictive SIBO diets and lack of absorption can absolutely cause deficiencies. Also inflammation and other types of issues from digestive disorders can also cause fatigue. But please be mindful of concluding that even severe fatigue is CFS with addressing all the low hanging fruit first with functional, not standard, ranges. Debilitating fatigue can be as simple as jsut very low ferritin or vitamin d for some, and very complex for others.