I see this number (BMI of 17.5) all over the internet, but only on pro-ana sites. Where did it come from? Mathematically it doesn't make sense, it's completely arbitrary. The diagnostic criteria for anorexia mentions "weight loss leading to maintenance of body weight less than 85% of that expected or failure to make expected weight gain during period of growth, leading to body weight less than 85% of that expected"

"Of that expected" means someone who was has a prepuberty BMI of 25 who post-puberty becomes a "healthy" BMI of 21 (assuming they meet the other criteria) is anorexic, but someone who starts out with a BMI of 18.5 and drops to a BMI of 17.5 isn't. Even though the second one is underweight the loss isn't significant enough.

I think it's a little detrimental for anas that are of above average frame size who maybe bottom out at a BMI of 18 and are suffering all the ill effects that others get at a BMI of 16. They'll have one more excuse not to seek treatment because they aren't even an "anorexic BMI" yet.

I weigh less now than I did when I was put into treatment. I went from being morbidly obese to the high end of healthy, while growing 3 inches taller, all in less than a year. I didn't consider it to be a problem because I was still fat. I got better, I thought anyway, and I lost more weight healthfully. But I've gained some weight lately, almost a decade since my treatment, and I find myself back on pro-ana sites.

This has kind of turned into half question half confession.

So where DID that number come from?

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