I realize my post probably offended some people. Thats not a bad thing. People need to be offended sometimes, it makes you think about it. You did ask for my honest opinion, and I have a Biblical reason for my thoughts. To go more in-depth, I did not say that fat people are not attractive, I did however say that most people see it that way. Whether or not people admit to being "shallow" is a completely different matter.
It may be presumptuous to label someone "shallow" who is or is not attracted to someone based on their looks. The way you look is a part of who you are. There are a lot of things I am looking for in a potential life partner, looks is one of them. If someone doesn't look attractive to me, I am not going to spend time on them because so far, everything I know about that person leads me to believe that they are not right for me.
God made men sight-based and women touch-based, and He made no mistake in making us that way. He made it so sight is our primary sense, having more weight than any other sense, even often our emotions. He also knew what every one of us will believe about what is beautiful and what is not. Knowing those things, He created us each with our own metabolisms, charismas, "strong" points, and "weak" points, creating all of them on purpose.
People say that you should not care about how others look because they were created that way, and that is true for the most part, however weight (the topic at hand) can be managed through self-discipline. I don't judge someone for something they can not help because I believe that God is a wonderful maker who creates beauty by His hands, and each person He creates is His temple. It is a personal choice, and I am not attracted to someone who damages that temple. To me that also includes people who get tattoos, dye their hair, or get plastic surgery. That is like telling God "okay, I see that you created me how You wanted me, but I think I can do better" .