That's the point it will not lead to weight gain. But according to CICO they should become fat, but they won't. And if this is possible by not having one hormone. That is quite a big discovery. The human body is way more complex then one hormone. And fat gain can be due to many reasons, another hormone could be cortisol, bad sleep, Obesogens[0].

If CICO does not factor in what is not stored or digested. Therefor it's a flawed model. Therefor it would be better to look at what is working, and wath was working before we got unto the low fat craze. In the 1950 up to 1980 bodybuilders where eating low carb high protein diets. Everyone was thin back then, just now we are returning to knowlegde.

But the thing is according to latest science obesity the focus is not on CICO anymore. Would be great if more people would be willing to conduct their own N=1 studies and try low carb dieet, keto, or intermittent fasting. It works the same way by keeping insulin low. It might do wonders.

[0]https://www.healthline.com/nutrition/what-are-obesogens

[1]https://www.health.harvard.edu/staying-healthy/stop-counting...