I'm going to be honest. I can't believe you're even asking this question with the popularity of songs like "Baby Got Back" and how much girls in music videos emphasize it. Here's the simple truth:
Most guys dislike runway models because they're sticks. Guys like curves, not sticks. The hourglass shape (big chest, small waist, big everything else below the waist) is the most desired body type for a girl to have with pretty much any guy.
Yes, it's a turn-off because a big behind is usually attached to an unhealthy body. The exception is if that area is just naturally more curvy than most girls without actually having more fat, in which case it's cool and can be a turn-on.
Being curvaceous is great. The girl I am pursuing now is curvy and I find it very sexy. What I don't like is when a girl is fat and her thighs look like cottage cheese. But curvy girls are sexy in my opinion.
Every guy is different. I know guys who won't even look at a girl who doesn't have a big ass. I know some that only like size 2s. It depends on him. So don't worry about what guys like because every guy likes different things.
a lot of guy like big butt,lips,boobs so don't worry I have a big ass and big lips and boobs this guy told me that if you have big lips it fun to kiss if you have a big ass it is better when you have a big ass and in boobs they like it a lot