The new formula had little impact among the medical community until long after Quetelet's death. While doctors had suspected the ill effects of obesity as far back as the 18th century, their evidence was purely anecdotal. The first large-scale studies of obesity and health were conducted in the early 20th century, when insurance companies began using comparisons of height and weight among their policyholders to show that "overweight" people died earlier than those of "ideal" weight. Subsequent actuarial and medical studies found that obese people were also were more likely to get diabetes, hypertension, and heart disease. (Of course, this later allowed the medical insurers to either invoke "pre-existing conditions" to bar people from coverage or, more often, have an excuse to increase their premiums.)
By the early 1900s, it was fairly well-established that these ailments were the result of having too much adipose tissue—so the studies used functions of height and weight as little more than a proxy for determining how much excess body fat people had. The problem with proxies, of course, is that they are not direct quantifiers or indicators and are only so good as the physical basis really allows.
Medical researchers , meanwhile, needed a standard measure of fatness, so they could look at the health outcomes of varying degrees of obesity across an entire population. For decades doctors couldn't agree on the best formula for combining height and weight into a single number—some used weight divided by height; others used weight divided by height cubed. It arrived in 1972, when physiology professor and obesity researcher Ancel Keys published his "Indices of Relative Weight and Obesity," a statistical study of more than 7,400 men in five countries. Keys examined which of the height-weight formulas matched up best with each subject's body-fat percentage, as measured more directly. He concluded that the best predictor came from Quetelet’s BMI: weight divided by height squared. Keys renamed this number the body mass index.
Further, the BMI is actually a solid example of the “proofiness” that Charles Seife referenced in his book, Proofiness: How You're Being Fooled by the Numbers.
In this regard, one of the surest signs of proofiness is the failure to provide attached uncertainties to the measurements - any measurements! Since BMI is always recorded as an absolute single number, say 29, and never as 29 + 2 or whatever, then it is inherently proofy - a bogus quantity. Seife emphasizes there can NEVER be a 100 percent accurate number if based on physical measurements, and he's right. Maybe the scale used is off by a pound or two, and maybe the height isn't evaluated for the associated probable error - based on the instrument used to measure it. OR......maybe, just maybe the presumed cutoffs along the BMI chart indices have been majorly distorted by earlier misclassifications in large epidemiological studies.
Alas, few doctors - including our own - have made the switch. This is probably because waist measurements require slightly more time and training to interpret than it takes to record a BMI reading and use some fake out chart, which doesn’t come with any “official cutoffs”. (Right now, my BMI is 29.5 but I laugh when anyone says I am “over weight” for the reasons given above, especially the proofiness of the index and nonsensical units.) The sensitivity of doctors to these slight inconveniences signals just how difficult it will be to unseat Quetelet's antiquated and irrational, proofy formula. See, the body mass index is cheap and easy to get (never mind the absence of uncertainty), and it has the incumbent advantage in that the Lords from On High in Health Central have conferred their benediction – along with the political-Pharma –lobby enclave – so who’s going to argue with them? Well, I am!
Sadly, just like tea leaves, natal horoscopes and palm reading, BMI is here to stay—despite its flaws – the chief of which is that it’s irrational and has no bearing to any real physical quantity (as the examination of its units discloses)
As for rationality in terms of obesity these are the key obesity- BMI myths you need to know, summarized from Prof. Paul Campos in his book, 'The Obesity Myth':
1) Weight is a good proxy for health ("97 percent false" according to Campos)
2) Health improvement comes via transition from being fat to thin. (Hardly ever, for most people - especially the elderly who are more at risk if they become frail.)
3) We know how to produce long term weight loss.
In respect of the last, Prof. Campos makes it clear that despite the bloviations of the medical-industrial-insurance complex and the government health brigade as well as the health diet faddists, no one really has a clue how to sustain long term weight loss. Yes, they say, "balance intake of food with exercise" -but if a lot of weight gain is traced to gut bacteria this is a non-starter.
Then there is the leptin factor, which hormone levels decrease when people don't get enough sleep - and which causes them to eat inordinately. As explained on one medical site (WebMD):
"When you don't get enough sleep, it drives leptin levels down, which means you don't feel as satisfied after you eat. Lack of sleep also causes ghrelin levels to rise, which means your appetite is stimulated, so you want more food,"
The sad fact is too many overworked and tech over- connected Americans are in this latter category. Dieting won't help them but getting on a regular, decent sleep schedule might!
Stay tuned, and in the meantime don't get hysterical over your BMI!