Britney Spears works hard to keep rear in shape

Britney Spears
Britney Spears Bang Showbiz

BRITNEY Spears has to work hard to keep her butt looking good now she's in her 30s.

The Scream & Shout singer has noticed changes in her body and metabolism since she started the third decade of her life and to keep her derrière in the condition it is famous for she has to exercise even more.

Talking about the changes to her rear, Britney told the new issue of Shape magazine: "I like it, then again, I hate it. I'm in my 30s now, so I have to work harder to keep it up."

The 31-year-old pop superstar - who appears on the cover of the publication - says her favourite way to keep trim is to do yoga every week.

Britney also credits the Nutrisystem weight loss programme - which is comprised of easy to cook, nutritional meals - for keeping her weight in check but she admits she sometimes struggles not to indulge in some of her favourite calorific treats.

The blonde beauty - who has two sons, Sean Preston, seven, and Jayden James, six, from her marriage to Kevin Federline - admitted: "Dieting is tough ... because my specialities are spaghetti, brownies and chocolate chip cookies!"