No one cares that much, my now wife was just heading over 400 before she decided it was affecting higher mobility and now watches she's stays around 280.
Don't get me wrong, there is that 1 in 10000 that's an absolute fuckhole asshat who thinks it's clever to comment, but it really doesn't happen much. You tend to look and think, yeah, you look like you're on crack, nice front tooth mate, what happened to the rest.
But there's your chance, your make and break. If it happens, show your appreciation for her. If you hear or see it, she will, engage with her, give her a kiss, it basically says 'fuck off pal' I like what I like.
I lost a couple of friends over my choice in partner. Both thought it clever to tell me the obvious, 'oh, typical fat bird again, except you've excelled yourself this time', then they meet her properly and realize she's the best, all the while despite giving me a small roast for it, couldn't help but stare at her chest.
One of them got ditched for not learning, and got a cold hard truth of I didn't go to Thailand for all my holidays to eventually come back with a wife that has the body of a ten year old boy. That didn't go down too well, haha.
TLDR, if you like fat girls, date fat girls. If you find your preference goes up, go with it. Just be prepared to do a lot more if you get serious with someone over 420, you need to compensate a bit for your preference, but what a fucking ride, literally at times