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What I am getting at is that most people are not able to initially grasp this nuance, and the fundamental fact is that there IS a threshold of calories where you WILL lose weight no matter what. It's up to every individual to work on their motivation, but frankly that's orthogonal to the facts of the matter, and it's better to be direct rather than tell half-truths because it's "complicated". I almost never see discussions of motivation and differences in metabolism in these types of threads elsewhere, and to just assume the average person understand these factors is a mistake. The first thing people need to learn is that cutting down food will lose weight, point blank. Then you can add on layers about metabolism and motivation as the journey continues.
Once you cross this threshold, the organism activates every failsafe evolution devised since the first metazoan arised, to ensure you stop and come back.
A properly calibrated body will just do what it's supposed to do. For the rest of us, it's an uphill battle.
Joking aside, being overweight is mostly about body density, not mass. Few people get upset about having too much lean muscle or the food inputs needed get there; that is a different set of health risks.
Whether your body converts incoming calories to muscle or fat or whatever else does actually depend (to some variable extent) on genetics, along with many other factors. Glossing this as “breaking the laws of physics” is a straw man.
Exercising a lot is generally healthy, but high impact exercises (running comes to mind) can cause your joints to wear out a lot faster.
This is all also assuming an average, healthy person with no existing medical conditions. Things get trickier if you have exertional asthma, any kind of condition that can cause fatigue, etc.
Exercise-related rhabdomyolosis (muscles break down => myoglobin overwhelms kidneys) is very bad.
Some powerlifting regimens are possibly related to heart damage, the causality isn’t 100% clear to me.
I think those reports are overblown, especially with little mismeasurements on the order of 1Tbsp of butter or the fact that many foods have labeled calories 20% less than the actual caloric content, all of that combined with thinking that exercise is more impactful than it actually is (especially weight training), but the core claims aren't totally ludicrous at face value.
When you look at how our hormones are affected by different types of macronutrients, there are dietary ways to restrict calories, prevent hunger from becoming an issue, and still maintain a decent level of mental acuity.
I've found that aiming for 150g of carbs a day and .7-1g protein/pound of body weight to be fairly self-regulating. I have to eat more carbs on days I do BJJ (pretty glycogenic sport, but, admittedly, has become less demanding the closer I got to my black belt), but using that target as a rule of thumb has worked out well for me over the years.
When we talk about CICO, there is the reality of our hormones that we have to consider--at least in terms of human behavior. There are ways to diet with ease and no discomfort, but yo-yoing between binging on snacks and trying to not eat anything isn't very feasible.
Starving yourself is not a healthy way to lose weight. It is not an effective way either, since you will either gain it all back when you decide to eat again or get an eating disorder.
>mice fed a HFD-CysF diet were able to lose approximately 30% body weight within 1 week despite maintaining a high calorie intake
Maybe things are more complicated than just conservation of mass.