This is something I don't touch on enough probably:
If you are eating just protein and fat from animals its incredibly important you eat until you are truly full every single day especially when you are first eating properly.
Trust me you will not gain fat, infact, you will actually increase your metabolism, lower your cortisol, and ensure you are getting enough insulin signalling from the protein.
A large mistake I often see is people going straight to my fat loss protocol or trying to "limit calories" in a diet that isnt upregulating the randle cycle.
Its important to understand that on this diet you are primarily consuming saturated fat, which is incredibly pro thyroid and it can actually be hard to not get shredded, so please ensure to never starve yourself when it comes to eating meat/eggs/ or butter.
Once you have been on the diet for lets say a month you will probably naturally get to around 12% body fat depending on your starting place, if you then want to get to that single digit stage ready leanness, then reducing dietary fat slightly and raising protein is a proper protocol.