Middleton, 30, an author and party planner, received media attention from around the world for her shapely appearance in the gown.
E! News said she joked at the Women in Advertising and Communications dinner in London Tuesday about her unexpected experience in the spotlight.
"As I have found out, recognition has its upside, its downside and -- you may say -- its backside," Middleton said. Referring to the dress, she said she was "glad it fitted."
"In retrospect, it fitted a little too well."