One thing I’ve noticed is that a lot of the advice that gets thrown around comes from the perspective of someone who is or once was obese and insulin resistant. That’s not to knock anyone here at all. The keto diet strongly addresses a set of issues that a certain group are likely to have. It fights insulin resistance and high blood sugar, so you have tons of diabetics here. High insulin usually results in weight gain, so you have tons of obese or formerly obese people here.
Going from that assumption, it’s easier to understand why someone might say CICO doesn’t matter. For them, it doesn’t on keto. They will experience a very sharp drop in insulin production very quickly. The hormonal model of weight loss says that this is going to cause them to lose weight down to their new set point almost no matter what quantity of food they eat. Now, let that same person stay keto long enough to lose all the weight their new insulin level allows, and suddenly CICO matters for them again. It’s at this point that they have to get creative if they want to lose more. They can restrict calories to lose weight, or they can fast to drive their insulin levels even lower. In fact, long term both of those approaches is probably doing the same thing. Lowering insulin to allow the body to shed pounds naturally. From what I can tell, the more manageable approach appears to be fasting, especially for someone who has been on a ketogenic diet for a while.
Now, let’s say you’re a relatively healthy, non diabetic, insulin sensitive person. You’re still going to benefit from keto in he form of hunger management, energy levels, cognitive enhancement, and continued weight management. CICO is going to matter to you sooner than the obese and/or diabetic person though, at least if you want to continue losing weight.
Of course the argument could be made that losing any more weight would be deleterious to your health. Your body has told you quite clearly what weight it wishes to be at. You’d probably do well to listen to it, even if that means giving up your dreams of washboard abs in the short term. Long term, you might just get those washboard abs anyway as a result of steadily increasing your insulin sensitivity and thereby reducing the amount of insulin your body produces. This is a long and protracted process however. It isn’t something to expect anytime soon without some of the more intensive methods mentioned earlier. All of those methods involve reducing what you eat, either entirely for a short period, or partially for a long period.