Britney Spears's rehab diet!

When 'Toxic' singer Britney Spears stepped out to do some shopping in Beverly Hills recently, just days after checking out of the Promises Treatment Center, the pop singer's clean and tidy appearance left onlookers amazed reports NW Magazine.

Wearing a simple, strapless white sundress, oversized sunglasses and a long brown wig, Britney seemed calm and composed as she shopped in a Victoria's Secret lingerie store.

The singers dramatic weight loss left gossips gasping.

Sources say Britney Spears used her time at Promises in Malibu to work on toning her physique.

"Britney vowed to do something about getting her body back in shape a few days after going into rehab," explains a source. .

"She watched everything that went into her mouth," says the source. "Most people gain weight in rehab, but Brit wasn't about to let that happen.