Hi sophie - on my 3rd round of X and I'm finding to get the ultimate results the clean eating is critical - that being said I do allow cheat day on recovery week. I'm travelling a lot on my new job so it's a lot harder - I certainly don't have it down pat.
I've met a few of the BB folks in person and man they are LEAN - not sure if I'd have the dedication. Phase I is really extreme but definetly effective in blasting the fat. For me... almost a year into it.. I've totally changed the way we eat. I always kept my weight under control by lower calories - I was NEVER focusing on getting enough protein. For me it works to focus on the protein for the meal. We've been eating a lot of chicken breasts, fish, chicken kabobs, white turkey burgers. I get almonds for my snacks. A big difference is the protein drinks tastes yummy and starts the day off right. Also love egg scramble - feta, spinach.
I try to keep close to a 2nd phase eating in phase I and II. The last week I haven't been great. Sounds like you have what you need if not let me know!