comment deleted, this is what it said.
This isn't correct. First, CICO is not a real thing because the human body is not a mechanical machine; it is wildly dynamic. If you were talking about a steel car engine with immovable parts, that's one thing. But the body is series of dynamic subsystems with wide tolerances - it can adapt to changes very well.
When you reduce calories, the body "fights back". Instead of maintaining 98.6 degree body temperature, it will hover a couple of degrees cooler - which saves like 150 calories/day. It may produce 2 oz less bile, which saves 75 calories/day. Throughout your ENTIRE body, systems will reduce load and run sub-optimally to account for the lack of calories in. Picture cuts like this being made across every subsystem across the body, saving hundreds or into the thousands of calories per day.
Second, if were to find the sweet spot and brute-force your CICO approach, it would be very difficult to maintain, and you'd have varying success. Your body will be actively fighting the restriction in ways you can't defend against (reducing the endocrine system, slowing the GI tract by 20% to extract more nutrients). A human body is a formidable foe and will strongly defend itself. Instead, there are more effective ways to lose weight.
A body can run on the "carbs/sugar" system, where carbs are translated into glycogen and your body runs off that. Or, a body can "switch" into a different mode where it runs off of protein and fat, where your body produces keytone bodies while digesting fat and proteins, and when carbs aren't available. Keytones are chemically similar to sugar, but are processed very differently. While in "ketosis", a body can "run" purely off of fat and protein (literally eating fat for energy), so long as sugar/carbs aren't present. tl;dr; - CICO (as people commonly talk about it) is a myth because the body is super-dynamic with MANY subsystems who can counter the attack, by drastically reducing the caloric need. It can and does turn the dials and knobs to account for a calorie deficit. It will use ALL of these controls to combat the deficit - and it usually wins. Second, CICO (if you were to find a happy medium) is difficult, rarely successful, and is not the best way to lose weight. A ketogenic diet is. This uses the "other" form of digestion, which specifically uses bodyfat for energy instead of carbs that were taken in through the mouth.