Britney Spears has lost a stone in recent months - but it certainly hasn't come cheap.

The star signed up to a £11,000-a-month diet and exercise regime after her bloated tummy sparked pregnancy rumours earlier this year, according to a report.

The mother-of-two, who eagerly showed off her slimmed down bikini body during a trip to Mexico over the weekend, is back to 9st after the stress of her custody battle saw her tip the scales at 10st 4lbs.

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Shaping up: Britney Spears showed off her slimmed down figure in Mexico over the weekend. The singer sparked pregnancy rumours after appearing bloated during a trip to Cabo in May

Her expensive heath make-over included £5,000-a-month on a nutritionist and diet supplements, £4,000 on a personal trainer and £2,000 on a private dance choreographer.

A source was quoted in Closer magazine as saying: 'She limits herself to 1400 calories a day with one 'cheat day' where she'll treat herself.'

'She also changed the way she eats, trying to have only two thirds of what is on her plate. It's all about portion control and fresh food now. And lots of water in place of Red Bull.'

Big spender: Britney is said to splash out £11,000-a-month on diet and fitness

She has also taken on some of Victoria Beckham's diet tips, eating plenty of steamed fish and snacking on edamame beans.

Britney also endures intensive work-outs with Pussycat Dolls' personal trainer James Van Daff as well as three-hour dance classes six times a week.

The source added: 'Britney piled on a lot of weight earlier this year. She was sho stressed about the custody case and her medication for her bipolar disorder  also made her put on weight. She was tired of being flabby and wanted to do something about it.

Now, says the insider: 'Britney is so proud of herself because her ab muscles are back'.

'She's feeling better than she has in ages.'

Shaping up: The singer hit the beach in a white bikini