The singer has been getting fit for her new tour

Britney Spears is well and truly back – and so is her body! A toned and trim Britney was snapped last week rehearsing for her world tour The Circus, which kicks off in March.

It’s four months until she arrives in the UK and we’re starting our countdown now.

The pop princess has managed to shed an impressive 1½st over the past few months. She’s been working hard in the studio with her dancers and choreographers, as well as pushing herself to do two-hour cardio and strength-training workouts three times a week.

Britney’s trainer Steven Boggs says of her routine, which includes shoulder presses and jump squats: ‘It’s a nonstop workout.’ Britney herself is absolutely thrilled with the results, saying: ‘I’ve had to work hard at getting my body back to where it used to be.’

There’s more to Britney’s transformation than just exercise. She’s also turned to meal delivery company Sunfare to revamp her diet, swapping calorie-laden fries and frappuccinos for a 1,100-1,200-calorie-a-day menu of breakfast burritos, barbecue chicken salad and turkey burgers.

The star is said to be feeling the pressure as she prepares for a gruelling four-month, 44-date tour. Our sources say she’s also worried about the long separation from her sons Sean, three, and Jayden, two.

Just last week, rumours emerged that Britney’s jealous of the growing closeness between her children and ex-husband Kevin Federline’s new girlfriend Victoria Prince, who’s been snapped getting to know the boys and cuddling them on several occasions.

To Britney’s distress, the cosy foursome even took a family holiday to the snowy mountains of northern California over the weekend of 17 January. The singer is said to be distraught that she isn’t the one getting to spend quality time with her babies.

Despite her sadness at missing out on mummy duties, Britney looks to be focusing on her other role of pop star. And she looks damn fine doing it.

See the latest pictures of Britney Spears in Now magazine dated  9 February 2009 – out now!