Gaining

Someone who likes to gain weight who has a partner who also likes to gain weight. They both gain and support and encourage each other.

So to comment or expound on what Dr. Feeder said. You are both a feedee/feeder. You stuff your SO and he/she stuffs you. My favorite fantasy!

Ned Fox

I think both of you are right. I chose "mutual gainer" as well since I am turned on by my own weight gain and women who gain weight as well. While I am not in such a relationship, the idea of being with a women who loves to eat as much as I do and where we both encourage each other and grow fat together is my version of heaven.