i see, it depends on the cause, if hypothyroid then not "functional" / nerve related.Not for everyone, no. When I had tested and confirmed SIBO, starch and fiber exacerbated it, simple sugars did not. I eliminated the SIBO by removing all starch and fiber from my diet. My overgrowth was caused by an underactive thyroid/hypothyroidism and intermittent fasting only exacerbates the condition.
by intermittent fasting i only mean wait at least 8h without snacks, not longer. but when digestion improves, i find it more beneficial to drink fruit juice in small amounts, like a snack all day long, it's much better absorbed than drinking or during a meal, but only if upper small intestine is clean. this is my experience at least.