Britney Spears is showing off her toned body on the cover of Shape, and she’s dishing how she keeps herself fit while she’s in her 30s.

The “Circus” singer, now 31, admits “dieting is tough” and she has to take extra precautions to “keep up” now that she’s getting older.

She told the magazine for their June issue of her body, "I like it, then again, I hate it," adding, "I'm in my 30s now, so I have to work harder to keep it up."

Spears, mom to sons Sean, 7, and Jayden, 6, with ex-husband Kevin Federline, also said she uses Nutrisystem to keep her dieting in check.

“Dieting is tough … because my specialties are spaghetti, brownies and chocolate chip cookies," she said, Us Weekly reports.

The veteran entertainer also dished about how she’s preparing for her upcoming residency in Las Vegas, saying “I’m doing 90 minutes of yoga twice a week in addition to a lot of cardio—hour-long sessions three times a week with my trainer, Tony Martinez.”

She added, “The [Vegas] performances won’t be simple—they’ll be a massive party from start to finish. And to pull this off, I have to be in top condition and running at full speed.”

image: Shape