Gorgeous Jessica Biel admits that her diet affects the way she looks and feels on set.

While working on her latest film, The A-Team, Jess craved healthy snacks in order to keep up with her 18-hour filming schedule, states contactmusic.com.

Jess said: "I really feel like food is a drug. When I'm not eating properly, I have less energy – my body looks different, which means it looks different on film. I want to feel I can go 18 hours on set, if we have to, working, working, working, and feel confident about my health. So when I'm working, I'm really disciplined. When I'm not working, I'm very undisciplined."

In an interview with OK! Magazine Jess added; "I love food, love it. But I'm really disciplined and boring most of the time. It's so true!"

So that's your secret Jess!