A dream is a wish that your heart makes, but one viral diet inspired by Cinderella is a nightmare in more ways than one.

Currently trending in Japan, the practice of calculating one's "Cinderella weight" has been gaining traction on Twitter in recent days, Marie Claire reports.

According to the site, one calculates their “goal” Cinderella weight by squaring one’s height in meters, then multiplying that number by 18. It's essentially aiming for a body mass index of 18, which the U.S. Department of Health & Human Services classifies as underweight.

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Dieticians are worried the unrealistic Cinderella diet is not only negatively romanticizing fictionalized body proportions, but also encouraging extreme dieting.

“When your BMI drops to 18, you're at a seriously high risk of losing healthy function of your body,” Australian dietician Lyndi Cohen told The Daily Mail.

“'Restricting your diet to achieve this low weight is dangerous and you may feel lethargic, experience extreme mood swings, grow unwanted body hair, find it hard to socialize, be at risk of fainting and lose your period,” she also said.

''There is very real chance that people can die from trying to achieve the Cinderella ideal,” Cohen added, recommending that those intrigued by the challenge seek help from a medical professional.

Revelist further described the diet as "a hair away from an eating disorder.”

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For their part, Twitter users are largely slamming the "outrageous" and dangerous fad.

This is not the first time Disney's glass-slipper-wearing version of the princess has found herself in hot water. The entertainment giant was criticized in 2015 for actress Lily James’ scary skinny waist in the 2015 live-action remake, Business Insider reports.

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