Gwyneth Paltrow works her ''ass off'' to look good.

The A-list actress spends hours a week training with her best pal Tracey Anderson and says the miraculous results are worth the blood, sweat and tears she puts into her workouts.

She joked to Britain's Marie Claire magazine: ''There's really no secret to the way my body looks; I work my ass off - literally! I work out with Tracey Anderson one to two hours a day, five days a week.

''It's hard, but the reason I stuck with it was because I really started to see my body change. I'd walk past a mirror and be, like, 'Whoa, what happened? Where's that thing that used to hang down to here?!' ''

Gwyneth also reminisced about her biggest beauty regret, claiming she wishes she had never dyed her hair in her teens for a film role.

The 41-year-old blonde sighed: ''I'll never forget the first time I dyed my hair. I was 19 and doing my first big part in a movie, called 'Flesh and Bone'.

''My hair was a gorgeous ash blonde colour with all these natural highlights in it, so when they told me I'd have to dye it I was devastated! Once you do it, you can't go back, and I've been trying to recreate it ever since.''