Diet change

I had to change my entire diet two years ago - it was successful - due to a reaction to entire family of plant proteins. I didn't develop a normal allergy at a certain point of life, but an entire metabolic syndrome which I dragged from birth. So it was either stop eating all of that immediately, or a graveyard. It took me three months to adapt and almost eight months to shake off all disturbances I had.

If you changed your diet how much time you needed to get in tune with it?