"The prospect of a hospital requiring job applicants to disclose private medical information (which is what the BMI is) seems laughable, and is itself probably against the law, even if bias against the hypothetically-unattractive would-be employees isn’t. But having read all the handwringing over the unfairness of a policy against hiring people who don’t look the “right” way, I think it's important to note that the BMI itself is a deeply flawed measurement of size, ability and health.
The Body Mass Index we know today has its origins in the mid-1800s, when Belgian statistician and “social physicist” Adolphe Quetelet devised it as a part of his efforts to describe the “normal man” of his era, both physically and socially. The original Quetelet index had nothing to do with health or obesity, but was merely a means of working out the average build of a typical male human.
Enter Louis I. Dublin, who over one hundred years later would oversee the development of height and weight tables in his capacity as vice president of Metropolitan Life Insurance Company. These tables -- familiar to those of us who grew up prior to the government adoption of BMI -- were based not on medical information but on actuarial statistics. Basically, the charts depicted the mortality rates of men based on height and weight, which was important information to an insurance company for rating life insurance policies (as knowing who is likely to “collect” -- i.e., die -- sooner is useful for running a business whose purpose is to pays out upon the death of the insured).
Both of these developments, upon which our modern Body Mass Index is based, were designed to assess mortality trends over large populations, not to predict health or wellness for individual patients.
Next, in 1972, obesity researcher Ancel Keys was working to come up with the best height/weight formula to predict body fat percentage. He landed on Quetelet’s formula -- “the weight increases as the square of the height” -- as the most accurate gauge, and it was renamed the Body Mass Index. "
See the entire article @ xoxoJane