The following is not an unsupportive post. Quite the opposite. It's intent is to educate anyone following the IP diet so they can stop worrying about something that doesn't matter.
This
study details where ketosis was induced but calories were set at maintinence levels thus no weight was lost.
To take this to an illogical extreme you can test this at home. Every time you drink an IP shake drink a half cup of olive oil (955 calories.) You'll stay in ketosis but your weight loss will grind to an immediate halt.
One can lose weight being in ketosis.
One can maintain while being in ketosis.
In my opinion you're better off not worrying about it because what really matters is following the diet protocol. Stressing about ketosis is counter productive in my opinon especially because there is no reliable way to tell whether one is or is not in ketosis.