Credit: James Whatling/Splash News Online

She may be a Duchess, but Kate Middleton is a commoner when it comes to her workouts.

"For as long as I've known her, she's never had a trainer," says an aide of the royal, who squeezes in three 40-minute workouts each week.

When in London, the slim, 5-foot-10 beauty visits Clarence House's small private gym for rowing, running and weight training. But when she's home in Anglesey, Wales, with hubby Prince William, 29, "she never works out indoors, regardless of how rough the weather is. She likes to go on hikes, carrying small weights for her arms. She says it kills two birds with one stone," says the palace aide, adding, "William joins her on weekends."

Kate, 29, keeps eating simple too. Though one pal says, "she hates dieting," she sticks to healthy picks like oatmeal, dried fruit and almonds. "Kate's not much into sweets," says the aide, "but she does love Kettle chips!"