Formula works out to 18 percent lighter than Japan Medical Association guidelines, but not everyone thinks it’s a problem.

Some dieting women in Japan have what’s become known in online circles as the “Cinderella weight” as their target. The Cinderella weight (in kilograms) is calculated by squaring a person’s height in meters, then multiplying that number by 18.

Plugging a few heights into the formula gives us the following combinations:
● 165 centimeters (five feet, five inches) = 49 kilograms (108 pounds)
● 170 centimeters (five feet, seven inches) = 52 kilograms (114 pounds)
● 175 centimeters (five feet, nine inches) = 55 kilograms (121 pounds)
● 180 centimeters (five feet, 11 inches) = 58 kilograms (128 pounds)

If those sound like especially low body weights, it might be because they’re actually 18 percent lighter than the weights recommended for women of that height by the Japan Medical Association. In other words, even by Japan’s already slim baseline (relative to other societies), the Cinderella weight reflects a remarkably light build. The Cinderella weight also works out to a Body Mass Index of 18, whereas proponents of BMI as a health metric maintain that anything under 18.5 is too low.

Nonetheless, the concept of the Cinderella weight, not so much as a standard but as an aspirational ideal, has endured among a segment of Japanese women. Recently debate about the formula has flared up again online, with some Twitter users speaking out against what they consider an unrealistic and unhealthy goal.

“Unless you’re an athlete, the body-fat percentage that you’d need for a BMI of 18 is going to have you morbidly thin, so if you’re thinking about hitting your Cinderella weight, you should drop the idea.”

“Ridiculous. A woman would have to remove all of her internal organs and have the impossibly thin waist of a manga character to do this.”

“I used to weigh my Cinderella weight, and then I noticed how disgusting it was when I could see my ribs so clearly.”

“If you’re going to weigh your Cinderella weight, get set not to stumble from slipping out of your glass slipper, but from malnourishment.”

“Here’s a question: Is there a Hercules weight for men?”

At the same time, there are also Japanese Twitter users who don’t think the Cinderella weight is always a mark of poor health.

“My live-in-girlfriend weighs exactly her Cinderella weight, eating the same things and leading the same lifestyle that I do, and she’s perfectly healthy.”

“I’m not trying to diet, but I’m lighter than my Cinderella weight, and when I have my physical the doctors tell me I’m in fine health. I don’t look morbidly thin either.”

“It’s not like weighing your Cinderella weight automatically means you’re just skin and bones.”

As with any weight loss plan, the best course of action is likely to avoid focusing on a specific numerical weight so closely that you lose sight of other key health indicators, and to consult a fitness and/or nutrition professional before beginning any intense weight loss plan.

Sources: Hamster Sokuho, Twitter/@nash_yhaa, Twitter/@demisefgo, Japan Medical Association
Top image: Pakutaso