1. Sometime around puberty, when I started noticing women in general. I liked the bigger ones by default, and slowly went from "bigger boobs and butt = good" to "I like stuffed/fat bellies" to "girls overindulging is stupid-hot and I wish I could help a nice one go absolutely nuts with it" . Didn't take long for me to not really care about skinny women, like the ones with a bit of pudge and really go nuts for the huge gals
2. Nope, stocky but not fat at all, and a cigarette smoker to boot. The smoking especially is notable, not because I have anything against smokers but because it brings back memories of meeting her at the airport several times over the years, her clothes always reeked of it. I would definitely still be with a fat smoker, but my brain would need a little time to decouple "cigarette smoke" from "seeing mom again" first. That or it'd boomerang and make me rock hard in the most Freudian situation ever, who knows
3. Taught me everything useful and practical I know, very much the masculine (think less "cute fictional tomboy", and more "someone's dad trapped in a female body") type of woman, bigger balls than most men in my life growing up. I can safely say she's about as far from the kind of woman I'm into as it gets, aside from wanting to be with someone who has their shit together and is a functional, independent human being when not doing kinky shit. I was raised by her to see healthy relationships as an equal-contribution deal, rather than the alternative "one person handles everything while the other is decoration" dynamic you see in a lot of bad ones, and anything less than a relationship where two independent people can function without each other but are happier together just seems deeply wrong to me. It's outright prevented me from finding the "spoiled useless fatty" fantasy hot, since I just know I would despise a woman like that on every level the moment post-nut clarity sunk in
4. Pretty sure I was always wired this way from birth, presumably the "I like em chunky" gene skipped a generation or two before hitting me like a semi going downhill. That being said, the usual formative experiences like cartoons featuring stuffing/WG/expansion and unrestricted internet access on my own personal computer definitely accelerated things to some degree. I vividly remember looking up ancient photos of clothed BBW models on google images as a kid, well before I fully understood what a fetish was or why big women made me feel a certain way
5. I'm at peace with it, and I've accepted that I'm gonna have to find someone of similar freakiness to share my life with if I want to be truly happy and fulfilled, assuming I get that far. Closest thing I have to a life goal at this point is "find a sweet lady who's into this stuff, and pour everything into making her as fat as she wants and happy as I possibly can". I did have a period in my late teenage years where I felt like a freak for being into fatties, but I eventually came to the conclusion that it's not my fault my brain is wired this way and it's pretty natural/"normal" in terms of kinks, especially compared to some of the really depraved and immoral options out there. If liking fat women is my greatest sin and deepest shame in life, so be it, I'm cool with that
6. They tend to fall into the same perception filter in my head as other men; I don't have anything against them, but they also don't make my dick hard and I have no real desire to see them naked. Now, that changes a hell of a lot if the thin girl in question is a feedee, but outside of porn I have yet to see anyone matching that description, especially as it seems like women are universally getting fatter over time. Not that I'm complaining, my point however is that I'd definitely still do things with a rail-thin lady if she was into this and intended to gain
7. (bonus no one asked for): I've noticed my size limit and what exactly I'm into about this whole fetish sphere has gotten much broader with age, for what it's worth. Early on I just found basic stuffing and chubby girls with a little bit of belly hot, then I later moved up to actual BBWs, then SSBBWs after that. While it's stabilized in my 30s to where SSBBWs are my "sweet spot", both in fantasy and IRL, I would still absolutely fuck a woman who's too fat to walk unassisted in whatever way possible, provided I ever got the opportunity and she was into it. For a serious relationship though, I'd want a girl who can still reasonably take care of herself and get around fine, as in an actual life partner who just so happens to be big, soft and happy with it
Also, as mentioned above, what exactly gets me going about this has shifted. It used to be simple caveman "bigger is better" logic, but over time it's become more about finding women who go all-in on sexual and physical indulgence attractive. A woman who just happens to be fat due to life circumstances and accepts it without being into it is all well and good, but one who actively enjoys being a gluttonous fatty because it turns her on is the holy grail for me. That element of "she'd be doing this regardless of whether anyone else found it hot, but also clearly likes the attention" is what takes fat-centric porn from "alright" to "HOLY SHIT" in my book, both real and fantasy. It's just not the same if she's not enjoying it as much as whoever is watching/feeding her, a feedee's pleasure is akin to tossing gasoline on an open flame in terms of much hotter it makes things to me
Back to the psych angle, I'm no expert but I think my fascination with this ties back to being a person who enjoys helping others in whatever way I can. Naturally, there's no sexual angle to it when I try to do nice things 99% of the time, but the specific scenario of keeping a nice woman full, fat and sexually-satisfied on a regular basis is apparently my brain's idea of truly-fulfilling success in life. Being able to provide for someone like that and see tangible, arousing results from doing so is like crack to my mind, the same good feeling of being nice and helpful but cranked to 11 and infused with raw sexuality
If I ever hit a point in life where I can easily afford to overfeed my girlfriend/wife because she's into it, make her fat as hell and enjoy the results with her, I'll be able to die happy knowing I won at life by my own definition