Isla Fisher worries her stomach ''will never be flat again''.

The 'Great Gatsby' actress worked hard to lose 70 pounds gained in pregnancy after giving birth a second time in 2010, but despite regaining her svelte frame, she isn't convinced her once toned tummy will be the same again.

Isla - who has two daughters, Olive, five, and Elula, two, with comedian Sacha Baron Cohen - explained to Fitness magazine: ''I gained 65 pounds with my first baby and 70 with my second. I had severe morning sickness both times, so I mostly ate super-size bowls of white pasta with loads of butter and cheese because that was the only thing that took away the nausea.

''I had to shoot 'Confessions of a Shopaholic' about three months after I gave birth to Olive, so the producer, Jerry Bruckheimer, hired a trainer to work with me three times a week. That was both inspirational and terrifying because I didn't want to let the trainer down. After I had my second daughter, I slowly lost the weight by breast-feeding, hiking Runyon Canyon [in LA] and working with a trainer every couple of weeks.''

The 37-year-old beauty has come to terms with her post-baby body, however, as it reminds her of ''greatest achievement'' - her two daughters with the 'Les Miserables' actor.

Isla gushed: ''Even though it will never be flat again, it's still my favourite [body part] because it reminds me of my greatest achievement: my babies.

''For me, so much about life is acceptance. You can look in the mirror and find a million things wrong with yourself. Or you can look in the mirror and think, 'I feel good, I have my health, and I'm so blessed.' That's the way I choose to look at it. I don't need to be perfect. I'm doing just fine.''