When making any kind of significant change to your diet, it’s best to measure things before, during and after the change you’re trying to make.
Later, when you’ve completed the change, and reached a point of stability at which it feels like measurement is no longer necessary, that’s fine. You can drop the scales, journals, and counting at that point.
But if you’re looking to effect a change, know that the action you took was in fact the cause of it, and make it stick, measure it closely.
Take measures to keep out all other confounding variables too.