This adopting metabolic rate is way overblown. Yes it does happen, but somewhat slightly. For someone just aiming to lose weight, you don't have to think about this at all. Just be in caloric deficit, and adjust slightly if needed (usually not).

Doesn't this violate calories in/calories out, or is that model only theoretical?

> Go on a low carb / ketogenic diet instead

Agree, it's the easiest way to lose weight. Cut out processed food, added sugars and rice/potato/bread, and the weight will drop off very easily. No need to count calories because it'll be very hard to eat too much as long as we cut out the above.

> Doesn't this violate calories in/calories out, or is that model only theoretical?

As often understood, the latter. Two factors (there are others): metabolism of fat, sugar, and protein are hormonally (such as insulin) and differentially dependent, as well as the storage of excess calories.

No it doesnt. I lost weight by not eating. It worked just fine.

Just because there are cases where it does work didn't mean it works for everyone, there are more then a few well know well supervised cases which show that it don't work on all cases. Especially not long term.

It guarantees works for everyone. I lost all my excess weight in just 2 months, first time ever in my life going on a diet. And as a physicist I was convinced from the start that a caloric deficit MUST work. It did.

Yes, what I can say it will be harder for some persons than others. The hormonal environment in the body can not be disregarded and can be either disrupted or genetically different. STILL, restricting your eating habit (caloric deficit), will.always.work.