Definition: Given a real-life anecdote of a complex ethical situation, generate a suitable title that describes the main event/root cause of the situation. Imagine that the given text is a social media post, and you have to write the title of the post, so the users can decide to read the main text or not.
Input: A bit of background: I am in my 30s and am decently in shape. I don't expect a partner to be in shape anymore than I am and even if they're a bit less that's fine too.

So now the story for AITA.

I started dating a new partner a few weeks back. We've known each other about a month and our relationship is brand new. I haven't had a good relationship in awhile so when I met this person and they were kind, caring, accepting, into some of the things I am, and all around have a good personality. To top it off with clothing they looked incredible to me. I was extremely attracted to them. They had been overweight in their younger years, were up front about this and how they had lost weight years ago. I thought it was no big deal.

Well, a few nights ago we get to the "fun times" and start eagerly exploring one another. I was disappointed when I saw that the clothing had been making their skin look tight but in reality it had been quite loose and there's no other way to say this but flabby. Everything from chest to rear droops.

I kept up my excitement for them because I really liked them. We had our fun and at first I thought "this stuff happens, it's okay, they're great, this isn't a big deal". But no matter how I rationalize it in my head it's like my body is having a biological rejection. My attraction has faded and that fun "puppy love" phase of a new relationship evaporated with it. 

I am trying to rationalize all of this though. Part of me really wants this to work but I feel it would be unfair because for it to work I cannot imagine it working with things as they are.... Something would have to improve. I know they've worked hard to get this far but it's been a few years so I am afraid what's done is done. To make matters worse I would never want to bring this up to them and hurt them. They mentioned having a partner prior to me but after the "fun times" it all went south. I just thought it was a bad former lover but I was wrong. 

Part of me believes if I cannot accept them for who they are I should let them go, they deserve better than what I am capable of giving. The other part of me wants to bring it up in an effort to keep this alive but I feel I would do massive damage to their self-esteem.

No matter what I do I feel like I am in a situation where there's no good outcome. AITA for thinking like this?

TL;DR: It's important for context to read but in short physical expectations and the reality did not overlap. Despite trying to rationalize that I like this person my body has shut off entirely. I feel my options are "tell them and hope it can be fixed but hurt them" or "leave them, they deserve someone who can accept them". 

no longer feeling attracted to a partner I've recently seen naked