Even though our 150 testers changed their diet within two days (with a 92% satisfaction rate), it is generally recommended to gradually switch to a new diet.
A 10-day period is generally assumed, where on the first day, 90% of the old food is given and 10% of the new food is given; on the second day, 80% of the old food is given and 20% of the new food is given; and so on.