The 38-year-old actress - who has a 12-year-old daughter Lily with former partner Michael Sheen and is married to director Len Wiseman - insists the way she looks on the red carpet takes a lot of effort.
Referring to Aerosmith frontman Steven Tyler, she said: "I don't roll out of bed like this. It takes a village. I tend to wake up looking like Steve Tyler, then somebody comes to help."
Kate credits yoga for maintaining her trim physique - but says she only took it up because of the relaxation time at the end of each session.
She admitted to Australia's Daily Telegraph newspaper: "There's a carrot at the end - I get to lie down for 10 minutes. If that part didn't exist, I wouldn't do it. .
"I always hated the idea of it - yoga and golf are similar in that people can become obsessive and boring about it. I never thought that would be me, but I do feel a lot better [for doing it]. And a happy side effect is that it lifts my bottom."