Anecdotes aren't data. Cornhs disease is know to go into sponteneuous remission in around 10% of patients for no reason what so ever for years to dacades at a time.

So if you have batch of a thousand people each going from one fad diet to the next you'd get around 100 of them telling you very loudly that whatever flavour of the month cured them. The 900 who didn't just move to the next fad.