Kate Middleton, the Duchess of Cambridge who is expecting her first child in July, is reportedly keeping her body fit during her pregnancy through yoga.

The 31-year-old who is expecting her first child with husband Prince William has employed an instructor to give her private yoga classes at Kensington Palace.

"Kate has a yoga instructor visit her at the palace," a source told Us Weekly, "Kate and Wills dog Lupo is also helping the Duchess stay active, with the brunette taking the little pup for walks a few times a week to increase her heart rate a little."

The mother-to-be is also reading various books such as guides on "how to be a good parent and how to stay healthy for the baby."

Kate Middleton, who was undergoing hypnotherapy to help her overcome eating problems related to morning sickness, is said to be having sweet-toothed cravings.

"She's got sugar on the brain," an insider said, "Chocolates, biscuits, cake." And while she sneaks off to a nearby Starbucks for a cup of decaf coffee, she'll sometimes pick up a sweet treat!"

Meanwhile, Kate has been giving relationship advice to Prince Harry who is getting serious with new girlfriend Cressida Bonas. The 28-year-old royal was seen cuddling the 24-year-old model last month while skiing in Verbier, Switzerland.

"Harry's so head-over-heels in love with Cressida, that with Prince William's approval, he's enlisted Kate's help to make sure he doesn't sabotage the relationship," an insider told the The National Enquirer, "Harry told Kate he really respects her opinion and guidance, and he's relying on her advice because Cressida is the woman he wants to spend the rest of his life with."

It was recently reported that the duchess and the 24-year-old socialite have been rumoured to be at war. Bonas is the half-sister to Prince William's former girlfriend, actress and model Isabella Anstruther-Gough-Calthorpe.