> It’s extremely obvious that doing something like running every day (if it leads to a calorie deficit) will make you lose fat.
But what if it doesn't because your body is a self-regulating dynamic system that changes energy partitioning and intake demands based on output?
The reason is, of course, that your body can downregulate energy expenditure according to energy intake. I've observed my body downregulate to about 1,000kcal/day. No fat loss on a 1kkcal/day OMAD diet for 2 months straight. No exceptions.
If you get below the bare minimum (say 1kkcal/day for me) your body will start shutting down pretty essential systems like the immune system, you won't be able to concentrate, sleep will be messed up.
Yes, I've done all these experiments, obviously.
So by "science", you mean your n=1 "experiment" and not conservation of energy?
Conservation of energy is a whole other story and I don't see how it's related to fat loss.
If someone isn’t losing weight on a caloric deficit, they’re not tracking their food intake and exercise properly.