Britain's Duchess of Cambridge won't need to work on her stomach much after giving birth as she has great "muscle memory".
The royal welcomed her first child, a little boy, into the world with husband Prince William this week.
Catherine continued looking great throughout her pregnancy and the new mother's trainer, Nicki Waterman, thinks she'll have no problems toning up now her little one is here.
"Pilates is great to get the core and stomach back into shape," Nicki advised British magazine OK!
"You need to do it twice a week, but Kate's super-fit anyway and she has great muscle definition and muscle memory, so her stomach should shrink straight back."
Catherine has always been known for her slim frame and didn't appear to put on much pregnancy weight.
Nicki wouldn't advise any major diets, but instead thinks the pretty royal should stick to healthy foods.
"There are so many rubbish fad diets out there, but it's simple, white sugar and flour will make you fat," she said.
"I'd advise Kate to eat eggs for breakfast as they're a superfood, for lunch any lean white meats such as chicken or fish with salad and vegetables and wholemeal carbohydrates like brown rice, quinoa and spelt. Obviously avoid alcohol too, but Kate will hopefully breastfeed, so it won't be an issue!"
Nicki finished by saying she believes Catherine will incorporate running into her exercise regime as "she loves it".
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