"I have worn butt pads ... lol :)" the singer, 29, posted on Twitter Friday.
After a Twitter follower sneered, "I highly doubt god's plan for you is bigger than your ass," Simpson -- who has been criticized for her fluctuating weight -- responded, "The G in the word God is capitalized. My a** is small actually."
Simpson is currently taping her VH1 reality show, "The Price of Beauty," about body acceptance.
