While I don't necessarily believe in the calorie balance theory where excess calories are always stored as fat, I do know that unless you are leaving a caloric deficit, your body has no reason to metabolise fat stores. So no matter what lifestyle you lead, you need to be giving your body a reason to burn fat. For carnivore part I, and the first week of carnivore part II I was eating meat ad libitum, and counting calories afterwards - seems my body (or at least my eyeballs) likes me to eat 2000-2200kcal per day. I wasn't losing any weight (except water), and I wasn't in ketosis for long periods - I'd tend to notice the taste in my mouth only when waking, or before dinner (I skip lunch most days). When I cut calories this time around, the weight started dropping immediately, beyond just the weight difference of food intake. Since I was already keto-adapted, it was a smooth transition into longer periods of fat burning, and I barely noticed until the scale made me think about it!
And speaking of ketosis - I ate dinner just under 5 hours ago, and my breath could cut down trees right now, but am I hungry in the slightest? Nope! Burning fat without starving? Awesome!
The bonus of caloric restriction in a low-carb way of eating is that due to the satiating effects of fat and protein, you are less likely to feel hungry as blood glucose is stabilised at a low level, and cravings are removed. Other than that, there is no fat-loss magic involved, as far as my research shows.
We do tend to eat less when we first switch to LC/VLC/ZC because the satiety of fat/protein-heavy foods helps prevent overeating, so we control calories 'spontaneously'. But personally, I can and have downed 150g of macadamia nuts when I'm not worried about fat loss - the bonus here is that I didn't put on any fat despite some skyrocketing intake figures! So caloric restriction = fat loss, but excess consumption does not necessarily mean fat gain, which is why I doubt the old calories in calories out argument, based on the science and my own anecdotal evidence.
I rarely feel hungry, unless I'm working particularly long days and routinely run more than 8 hours between meals. Even then, while I do feel hunger at that point, I do not notice any real dip in energy levels; thanks to keto-adaptation, my body is burning fat whenever it can, so it relies on that to keep me going. I reached ketosis when I was limiting my carbs to 20g per day, so ZC isn't necessary in that respect, but if I'm eating enough food to fuel my body without it needing to burn fat stores, my body then switches out of ketosis and it can be a struggle to get back to that point.
I suspect that I could go back to eating 20g carb worth of veg, at the same calorie limit, and continue to lose fat, but I feel so much better on the all-meat diet that I have no real reason to switch just for the sake of it. I do feel great on generic 'Primal', but amazing on all-meat. No digestive issues, no water retention, etc.
There are loads of excellent blog posts from experts regarding this issue, and it has been a particular interest of mine, yet I hadn't really put it into practice to prove it to myself until now. I am wary of metabolic slow-down, so I might cycle in a day or two of 2000kcal once a week if I see the fat loss slowing, but for now I feel incredibly comfortable (although I probably should start munching on mint leaves so people I talk to are also comfortable!).
Anyone care to share their experience?