Francisco d'Anconia said:
If you were in the midst of your cutting session while your body was in ketosis you have just screwed yourself royally, basically you'll have to start over to get your system back into burning fat instead of carbs (ie. controlling your insulin).
if in a ketogenic state or a reduced carb state (basically where glycogen is very low) then the last thing your body is going to do is use those carbs as fuel. it will shove them right into the muscles, supercompensating in this way. the sudden increase of carbs will also pull in the associated water bloat etc etc but the bottom line is that these carbs aren't being used as fuel (or going to bodyfat) because the body is craving homoestasis as always and will not use these as fuel if it's been used to using fat for an appreciable amount of time. if it's using ketones as energy then it won't suddenly switch to using carbs (glycogen), it will instead push the newfound glycogen into the muscles - this effect is manipulated by precontest bbers to get their muscles looking 'full' after being depleted so close to a show, they go low carb for some days then suddenly increase carbs - the body doesn't store these carbs as fat but puts them in the muscle. (also cheat meals tend to be high in sodium, another micro manipulated by bbers but that's another story)
now if you were to constantly high carb then the body would switch back to burning carbs but in this case it's a rare occurrence (relatively, eg once a week or once every 10 days) so it's not going to be enough to stop the body burning fat for fuel.
I confess that I've had no direct experience with PURE ketogenic diets (zero carbs, every day) but I use the above methodology for targeted ketogenic diets which include daily carbs, postworkout carbs etc and it works just fine. fat loss is usually BETTER when cheat meals are involved.
plus you can stay in ketosis even eating carbs every day (how many depends on the person).
now if you're having a cheat meal means it becomes a cheat day, then a cheat week, then a cheat month, well, perhaps it's best you don't cheat - on that self control issue I agree with you.
my cheating lasted the first half of the day, now I'm back on the proteins+fats after the cutoff, got a chicken stir-fry planned with a pile of chinese veggies (except water chestnuts, EW) and a couple of dollops of peanut butter* prebed.
of course all this is individual and these are just my personal observations and opinions, if you know something that works for you do it .. but in general having a cheat meal once a week or whatever is going to do more good than harm in most cases.
basically
alvatore got it spot on - unless you're trying to get down to 6% then there's no need to adhere to a strict diet with no room for cheat meals. especially if you feel deprived, you should never feel that way, ever. the best diet is the diet that doesn't feel like a diet.
* - on that note, I've recently discovered that natural pb is a good sleeping aid. if you have trouble getting off to sleep try some.. might just be me but you're not losing anything to try it.