Being in denial about this fetish for most of my life and finally just admitting I'm into it, I've thought about where it comes from quite a bit. In my feeder pov, this fetish is just a intense desire to care for your partner manifested. You love them so you nurture them.
Humans a products of their environments and for thousands of years humans were nomadic hunter-gatherers, food would often be scarce so when you finally came across a food source it would be natural to try to "push" as much into your significant other ensuring they don't die before you come across the next food source. I think it's natural to find a woman who can really pack it away attractive because your monkey brain realizes she would more likely be able to survive starvation periods where food couldn't be found, "get it while the getting's good" so to speak. (Plus chubby women are better to cuddle when it's cold ). Basically your subconscious realizes that being with a larger woman is a safer bet in the long run because she would be less likely to die.
The "piggy being degraded" stuff that some people are into is just mixing feederism with other fetishes, like masochism and exhibitionism.
I don't know about the rest of you, but I can still be attracted to skinny girls, but I def try to ask them to gain/bloat if we get together and make it clear I like it, I'm just upfront about it. It's just how I am and I've accepted it. Been in denial about it for too long and it just feels better to be honest with people. Plus it's great to fondle a girls belly pudge all night without making her feel self conscious about it because she knows you are into it and find it sexy. Honesty has gone a long way for me with this fetish and I've been surprised how many girls are either into it or okay with it when you are just upfront about it. A few get put off by it, but it's better to find your differences early on in the relationship rather than later down the road.
This is my $.02 anyway.