I started to shower cold (actually first warm, then cold, then "neutral") every day when I was 9. I'm 30 now, so 21 years of that :).

I almost never feel cold, when I do i'm sick or very tired.

I do martial arts and I gain muscles very very easily, so maybe that's because of that?

And all my blood values have always been in the optimal range, except cholesterol which is always a bit too high (runs in the family).