Gaining

yes it's possible. you'd be a mutual gainer, just like me

Of course you can. In particular lots of people have the desire for both, although in some cases they'd still prefer to focus on just one side at a time, while others would rather be mutually gaining. To make a ridiculously broad generalization, if you like power transfer associated with the gaining process, you probably want to focus on one side at a time, while if you just like fat and getting fatter then mutual gaining is more apt to what you want (but like all generalizations, there will be exceptions)

Long of the short, yes you can be both. I have a few feeder tendencies myself that I've been noticing more lately...yet oddly I'm still much more attracted to slim girls than I am larger ones.