Calorie counting is well supported by the studies in which people stay in metabolic wards and are fed a controlled calorie-counted diet. This is close enough to regular life experience to be meaningful, and would disprove your assertion that it's simply chance. You, on the other hand, bring up a lot of fairly extreme situations (immune system fighting an infection, cancer, shutting down the reproductive system), which simply do not happen nearly often enough to be relevant here. So the comment you're replying to is not "simply wrong".
It is not close enough to real life. The controlled calorie counted diet given to you by doctor is also designed to contain all iron you need, all vitamins of all kinds you need, fiber and so on. It is not random person food minus whatever that person finds easy or reasonable to kick out.
The people in metabolic wards are also not expected to be performing in work simultaneously, they are not expected to perform family duties or handle stressful situations reasonably. That also makes it massive difference against normal life where needs like this contribute to peoples failure to keep perfect diet.
watwuf already said it nice, that is anything but real life. Not counted in is that there is also very serious selection criteria (so, not random people).
On the other hand what you call extreme situation is nothing like that - most people have some type of chronic problem.
The most improtant aspect is certainly longevity of treatment - callorie restriction can not be followed - it can for some time, but soon enough (months or years) you will sucumb. Its simply not a normal way to have a life. It must be sustainable life practice, not something you apply from time to time.
