The reason why this is quite simple, body is unable to see the difference betweenexercise and staying alive in a hostile world. As such staying alive will always be prioritized. If CICO would work then we wouldn't be obesity pandemic[1]
[0]https://en.wikipedia.org/wiki/Sympathetic_nervous_system [1]https://pubmed.ncbi.nlm.nih.gov/28292617/
For me, after I exercise, I get ravenously hungry and am unable to concentrate for the rest of the day unless I eat a 3-5k calorie meal. I heard it would get better over time, so I did it for a year, one hour with a really good personal trainer, three times a week. It put a lot of strain on my relationships, and I got in trouble at work since I was basically at half capacity, and couldn't get any work done on Mondays, Wednesdays, or Fridays. I did it for a year and it was the same the whole time. I was also told that eventually I would get "addicted" to exercising, but I hated every moment of it up to the very end.
After a year of that, I stopped, and regained my sanity for the most part. I didn't actually lose much weight, but towards the end I had gotten some compliments about looking healthier, which was nice, but not worth the psychological tool it took on me. I guess I'm just sitting here desperately trying to not destroy my body further while I wait for some miracle cure for leptin resistance or something.
3k-5k calorie meal? That's an entire day's worth of calories, for someone really active. Strange your body didn't adapt.
Eating all that in one meal would require some extremely unhealthy eating, for me.
I know sumo wrestlers and other extreme athletes are capable though.
If GP is eating that much, they are very overweight. You don't burn that much calories during exercise, unless you are running a marathon (which I would not recommend doing 3 times a week).
This isn't universally true.
Exercise significantly decreases my appetite for about 3 hours post exercise. And for me, it's not just a barely noticeable decrease - it's an extremely noticeable long-lasting appetite decrease where I'll often end up skipping meals.
Do a quick google search for "exercise decrease appetite" for supporting evidence.