Slow metabolism is a bit of a myth. By that I mean that it's not strictly wrong to say someone has a slow metabolism, but metabolism is an expression of your activity level so what you're really saying is the person is sedentary. If the person starts being more active their metabolism will necessarily increase.

So, slow metabolism is not a disease, it's not a genetic disorder, it is simply a result of the fact that someone is spending too much time on the couch.

I think this gets lost a lot when people talk about "slow metabolism", they turn it into this thing they're just helpless to influence, like they're just cursed with a slow metabolism and that's that. It's not like that at all, which is why I don't like the term. It just hides the reality of the situation.

What is all that based on?

Knowledge and understanding.

So nothing.