Given the observational evidence that it doesn't work, what are you really asking?

Imagine a computer with a primary source of power, and a backup supply. You're measuring CICO of the primary supply. And you're tightly regulating the power available on primary to keep a power deficit. Unfortunately, during periods of high load, this computer is able to switch to the backup supply which you aren't able to exert tight control over.

There's a huge number of things that could cause a human to ignore their best interests. Ignorance to consequences, the long-term implications of any decision, degraded mental health, external social pressures, the list goes on and on.

Humans have impulses just like every animal, and proper training can convince a dog not to immediately lunge and eat every morsel of food they can smell. but it takes a lot of work and external pressure to train that into a dog, and even then given the right circumstances a dog will still eat food above their caloric needs. Humans behave the exact same way.

> it's easy for me to regulate my weight using cico, so obviously it should be easy for everybody

I know that's not the claim you're making, but it seems like it is and it is the one many other people in this thread are making. just like it's easy to train some dogs than it is train others. it's easier for some humans to control their caloric intake than it is for others.

CICO doesn't work for most humans. Claiming otherwise is on par with the saying just run this IOS app on Android it's easy it works for me! Perhaps a sufficiently capable engineer could make it work, but most humans aren't sufficiently capable.

I mean, it works in the sense that if you keep your calories out higher than your calories in you will lose weight.

Studies show that it's basically impossible to know your calories out without indirect calorimetry (and updating it regularly, no less, since your BMR + NEAT can vary significantly over time and in direct response to contemporary efforts to lose weight) -- and studies show that humans are dreadful at estimating their calories in.

So yes it works in a lab setting where your CI is pre-portioned in the form of milkshakes and your CO is measured via calorimetry. In reality though it makes people hella hungry and your hunger tends to increase in excess of changes to body weight.

Which is why the average weight regain after loss is 80% over 5 years.

So naturally it would seem we would look to develop ways to reduce our CI subconsciously. Enter GLP-1s. This is literally all they do. They reduce your hunger so your CI remains below your CO which studies show almost nobody can do without help.

Yes some people are genetically going to lose 200lbs and become the head of Weight Watchers in the same way that some people are going to win the olympic gold medal in swimming. That doesn't mean that you are going to win an olympic gold medal in swimming and it certainly doesn't mean that if the average person follows Phelps' training plan that they'll get an olympic gold medal in swimming.

Ultimately a treatment that works but nobody can actually maintain is a treatment that does not work. Hence GLP-1s. The question is why they are unable to keep their CI below CO. Not whether that’s how they lose weight.