Secrets of the stars' bikini bodies: How do Rihanna, Myleene, Mariah and co look so good? Our favourite celebs make having a beach body all year round look easy, but how do they actually do it?

Jessica Alba

Age: 31

Height: 5ft 7in

Dress size: 8

Secret diet weapon: Bootcamp training sessions, fresh fruit and veg

Jessica Alba is no fitness fanatic. The actress admits: "I'm not a workout person. Every single day I tell my friends we're starting a regimen, and then it's like, 'Want to get dinner? Want a glass of wine?'"

But she enlisted the help of LA fitness studio Barry's Bootcamp to get fast slimming results after giving birth to her second daughter Haven last year.

Each workout consists of high intensity cardio intervals and strength training for an all-in-one session that saves time.

Jessica, snapped in Mexico, alternates between this, a treadmill, swimming and yoga.

She also eats a healthy diet. "I think you have to eat in a way that makes you feel your best," she says. "I include a lot of veg, lean protein and fruit and grains in my diet."

She also believes in the importance of sleep: "Listening to your body is the way to tell if you're skipping a workout because of a lame excuse or because you need a rest."

Rihanna

Age: 24

Height: 5ft 8in

Dress size: 8

Secret diet weapon: The 5 Factor Diet and crisps

Rihanna lost a lot of weight at the beginning of last year when she went on the 5 Factor Diet and started working out with LA-based trainer Harley Pasternak.

His exercise and eating plan is based on fives. It involves five small meals per day, five days of exercise a week made up of five phases, each five minutes long.

Each meal has five specific criteria and the plan allows you five cheat days in five weeks.

Rihanna does cycling, stationary jogging and jumping jacks as part of her cardio routine. Most of her exercises can be done in her hotel room or backstage before a show, allowing her to squeeze exercise into her hectic schedule.

The 24-year-old singer from Barbados does, however, stop dieting when she goes on tour.

At her slimmest, the singer went down to a US size 0 - a UK size 4, but Rihanna missed her curves and has now gained some weight.

She maintains her figure working with Pasternak, who says that the singer now works out three times a week for around 25 minutes.

She also keeps in shape when she's on holiday using a cross trainer, but she's no longer watching her calories - and famously snacks on Cheetos crisps.

Mariah Carey

Age: 42

Height: 5ft 9in

Dress size: 8-10

Secret diet weapon: Jenny Craig's weight loss plan

Mariah Carey has had her share of weight loss struggles over the years, but since giving birth to twins Moroccan and Monroe last year she's in great shape.

The singer, shown here in Oz, puts her weight loss down to consistent exercise. "I worked like a fiend," she says. But she added that most of her weight loss is down to diet.

She says: "Since having the babies, 90% of losing weight comes down to my diet."

Mariah has followed the Jenny Craig weight loss plan since July and is now the company's spokeswoman.

"I feel better in every way," she says. "To me it's mind, body and soul. I was in a bad place during my pregnancy."

Mariah toned up by doing 45-minute aquaerobics sessions four to five times a week, and by walking. Following her pregnancy, she lost 30lb in three months and has now shed five stone. Rather than weighing herself she judges her size by how she feels in clothes.

Myleene Klass

Age: 34

Height: 5ft 4.5in

Dress size: 6

Secret diet weapon: Heartbreak diet

Following the break-up of her marriage to Graham Quinn last year, Myleene has lost a dramatic amount of weight.

The mum-of-two, 34, pictured in the Caribbean, has dropped two dress sizes and people continually ask her how she got back in shape.

The sad truth is that Myleene's weight loss is down to loss of appetite. Over the years she has struggled with her weight and has been every size up to a 16.

"People look at me and think I'm a perfect size 8, but I'm not naturally slim," she says. "I've got a mixed heritage and have hips and boobs - I'm always going to be a big girl trapped in a small girl's body!"

At her heaviest she went to extreme lengths to hide her body.

"I remember performing in Hear'Say at the Brits in 2001 and I had to undo the button on my size 14 trousers because they were too tight," she recalls.

Myleene used to indulge in pasta and pesto with cheese followed by chocolate bars, but in 2010 she slimmed down to a size 8 by walking and doing sit-ups. She also changed to a healthy diet of scrambled eggs for breakfast, sushi, salad or a wrap for lunch and pasta for dinner.

She has said: "I'm an emotional eater so I have to be careful or I could easily put on weight."

Myleene looks great , but we prefer her at a healthy size 8. Let's hope she finds a happy weight soon.

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