A nutrition expert has told Radar Online that LeAnn Rimes could be suffering from 'pre-wedding stress' after reviewing new images that have appeared of the country superstar.

The latest photographs show Rimes, 28, looking super skinny as she stepped-out with her fiancé Eddie Cibrian, 37, in Calabasas, California, at the weekend.

Dressed in denim shorts and a baggy black t-shirt, the once toned performer had bony shoulders and stick thin legs on display.

Dr. Farid Zarif viewed the images of Rimes and compared them to ones of the performer from December of last year.

The health expert said: "Just as a lot of people have a propensity to gain weight others have the same ability to lose it too.

"There is definitely an apparent difference in her appearance and stress could be a factor with her wedding coming-up.

"A lot of women try to lose weight to look good in their wedding dress and somebody like LeAnn Rimes is under 'invisible pressure' to look a certain way for her fans also.

"In addition she is under more stress because she is constantly being followed by photographers and unlike the rest of us her appearance is constantly documented.

"It could be that she feels better and has more energy with her new shape and at this point I would not say the weight loss was alarming.

"If I was treating her I would find how many calories she was getting each day and make sure she was getting a healthy balance of protein, fat and carbohydrates in her diet."

In October the 28-year-old told Shape Magazine that she keeps herself in shape by boxing and circuit training.

Credit: Radar Online

A newly-engaged LeAnn Rimes flaunted a noticeably bustier figure Thursday while sporting a teeny bikini during her vacation in Cabo San Lucas, Mexico with fiance Eddie Cibrian, 37.

"She recently got a boob job," a source reveals to Us Magazine. "She’s always, always been insecure about her size. She was a small A-cup. She often talked about wanting to get implants. She’d say, “I just want a little bit so they’re proportionate to my body.'"

The singer, 28, flaunted her new look while celebrating her engagement to Cibrian. "Cabo!!!!! Sun, bikinis, friends, food, tequila...celebration!!!! Gonna be the best trip!!" Rimes tweeted.

Rimes admitted to Shape last year that she works hard to maintain her picture-perfect bod.

"I'm a competitive person in a lot of ways, so I like a little bit of pressure," she told the mag. "It makes me get to the gym sometimes when I don't want to go, so in that respect it is good, but I try not to let it rule my life."

Credit: Us Magazine