Jessica Biel has admitted that she felt nervous about appearing in her underwear in her new movie.

In her latest film I Now Pronounce You Chuck and Larry, Biel was asked to film a scene which saw co-star Adam Sandler feeling her breasts.

"I was definitely freaked out about filming that scene where Adam has to inspect my boobs to see if they are natural," Jessica told Style magazine. "I knew it was coming, I thought: 'I've only got a month, three weeks, then two weeks.'

"I had to train pretty hard and stay on a structured diet. I don't like the word 'diet' though, I just kept my eating in check to get to a place with my body where I felt, 'OK, its cool, I can be in a movie in my underwear.' "

Biel is currently dating 'Sexyback' singer Justin Timberlake.