Fasting for any length of time is dangerous for pwME; because of our abnormal metabolism we very rapidly go into ketoacidosis, which can overwhelm our already poor kidney function, push injured muscles into rhabdomyelosis, and even wind up aggravating cardiac problems. It's basically a catabolic state which is the last thing we need! That's not even considering such "luxuries" such as cognitive function.
Of course acute fasting is sometimes unavoidable, such as bowel infections or surgery, which are difficult enough.
Better to try a sensible elimination diet, maybe try replacing some foods with juices etc, look into supplements that help with leaky gut & dysbiosis, but we need to eat to sustain base level functioning, there's no "reserve" because we're overworked or virtually overworked at rest (high "Resting Energy Expenditure").