General

I mean, I wouldn’t equate telling someone you have a weight gain/fat kink to “coming out” as while it’s uncommon, it’s not controversial or something everyone in your life will know or notice. It’s a small, secular detail to you that overall doesn’t really impact you daily on the scale that being gay, trans, or other things you “come out” for would be?
Either way, it’s not that big of a deal, share it or don’t. I personally don’t, but there’s no need worry if you do.

Speak for yourself. Everyone in my life knows I only go for chubby or very fat men. My friends (we are all very open with each other) know I am a feeder specifically.

Obvi, I don't tell my family about my fetish, but when I introduced them to my (at the time) 500 lbs partner, no one thought it was unusual for me that I was with such a large person.