Isla Fisher says converting to Judaism was the ''right fit''.

The 'Wedding Crashers' star studied the religion for three years before completing her conversion in 2007 ahead of her 2010 marriage to Sacha Baron Cohen but she insists she found the transition easy because the faith reflects her love of ''family and food''.

Isla - who has daughters Olive, five, and Elula, two, with Sacha - said: ''It takes a couple of years of studying. I've always been really into family and food, so culturally it was the right fit for me.''

The 36-year-old Australian actress has a slim figure and she admits she watches what she eats, but isn't too cautious about her diet and never worried about piling on the pounds during her pregnancies because she knew she would lose the weight afterwards.

She told Women's Health magazine: ''I do watch my food. But I've been blessed in that I never had any body issues during pregnancy. I loved being able to eat whatever I wanted and the whole experience of giving life. And I never worried about losing the weight afterwards, because breastfeeding burns all the calories up so fast. Breastfeeding - that's my big slimming secret! That and Spanx. Any time anyone compliments me on my figure, I'm wearing my Spanx undies!''

Though she is careful about her diet, Isla isn't very good at taking care of her appearance.

She said: ''I'm not actually very good at the maintenance thing. I don't buff, exfoliate, pluck, rinse, moisturise, suck, bleach ... whatever all those women do. I don't have vajacials. Have you heard of those? It's like a spa for your vagina!''