EXCLUSIVE: She's shedding for the wedding!  The slim down secrets Mariah Carey is using to drop 20 POUNDS before her big day (a glass of red wine included)

'I gotta shake you off' has a whole new meaning for Mariah Carey - that's because the superstar is on a mission to shake off weight before she heads down the aisle.

'Mariah is so excited about her wedding,' a family friend reveals exclusively to Daily Mail Online.

She is busy making plans for her third marriage to Australian billionaire James Packer, 48, off the coast of his homeland in August.

The family friend says Mariah is on a strict protein diet because she desperately wants to lose at least 20 pounds.

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Haute cuisine: Mariah, shown here arriving in Estonia, is flying high with her upcoming nuptials. The singer, on her Fantasy Tour, is on a strict protein diet because she  wants to lose at least 20 pounds in time for her August wedding

Showstopper: 'Mariah says she has to be very disciplined because she wants to take James' breath away when he sees her for the first time in her wedding gown,' a family friend tells Daily Mail Online exclusively

Pass the protein: Mariah is sticking to eating fish, chicken and chili beans, with ground turkey or beef to help her shed weight ahead of her upcoming wedding to Australian billionaire James Packer this August

'Mariah is only eating four ounces of grilled chicken, lean beef or one of her favorites, broiled Chilean Sea Bass or grilled shrimp with grilled asparagus,' tells the family friend.

Since Mariah never gets up before 11am - she skips breakfast, but has a smoothie or protein shake by noon.

The rest of the day she eats five small portions that include a salad with chicken or grilled salmon, while constantly sipping on Fiji water. 

The friend adds: 'She is also eating some of her favorites like baked salmon, chicken salad - with light mayo or mustard - and sushi.

'Mariah also loves cheese, so sometimes she will have some Brie on low fat crackers as a snack.' 

Not being cut out - red wine. Mariah was told she could have one glass a day and she does -  every evening with dinner.

'Mariah hates dieting because she loves to eat and she in Europe right now on tour, so it's difficult to stay on course with so much wonderful food around her all of the time, but she wants to have an hour-glass figure so she can have a very tight, sexy, figure-hugging gown,' a friend reveals.

'Mariah says she has to be very disciplined because she wants to take James' breath away when he sees her for the first time in her wedding gown.'

Which she has already began picking the exquisite fabrics out for - in addition to her gown for the rehearsal dinner and the one she is going to wear to the lavish reception.

In January, Daily Mail Online learned she had met several designers including a 17-year-old fashion student - Sabrina DeSage - who is studying at the Fashion Institute of Design & Merchandising in Los Angeles. 

Mariah Carey is renting a home in a gated community in Calabasas, California

 Mariah's home is currently being renovated so she moved out until it's completed

Figure flattering: Mariah Carey has already eyed up a gown, which has hundreds of gold butterflies, all sewn with 14-karat gold thread (left), to wear on her wedding day. Billionaire James Packer proposed with this 35-carat diamond (right) in New York City in January

The dress she designed has hundreds of gold butterflies, all sewn with 14-karat gold thread, flowing down the back of the silk gown and through the train. It's estimated to cost about $500,000. 

The family friend adds: 'Mariah says this will be her last marriage, that the third time is a charm, so she is determined to be the most beautiful bride the world has ever seen.'

Mariah married music executive Tommy Mottola in 1993, but because of creative differences and, according to Mariah, his controlling nature, the couple divorced in 1997. 

In 2008, Mariah married comedian Nick Cannon in The Bahamas - giving birth to their fraternal twins, Monroe and Moroccan, three years later. But in December 2014, Nick filed for divorce. 

Carey and Packer went public with their relationship last June and got engaged in New York City in January. Packer proposed with a 35-carat diamond.

This will also be James' third marriage. His first wife was swimsuit model Jodhi Meares but the two divorced in 2002.

His tied the knot with second wife Erica Baxter, with whom he has three children with - daughters Indigo and Emmanuelle, and son Jackson.