Returning back to old eating habits is essentially a very
wrong move. Weight loss through a LCHF diet is fast as compared to other diet
so basically yes, chance of regaining weight is to be expected.
There is no evidence that a LCHF diet leads to carb
intolerance.
You can however have a one
day “cheat day” once in a while which may lead to adding weight or stopping
your weight loss. This happens because you go out of Ketosis mode and start
burning sugars again. Usually it will take you 3 days after you stopped the
carbs to get back into fat burning mode.