BMI or body mass index is a number that is generated by dividing someone’s weight in pounds by their height squared and multiplying the result by 703. This simple ratio of weight and height is now used as a measure of health. And that’s a problem.
Belgian polymath Adolphe Quetelet devised the BMI equation in 1832. He created the formula to be used as a statistical tool across large populations, he never intended for the number to be used as a measure of individual health. When people say that BMI is a poor measure of health, that’s not accurate. The truth is that BMI is not a measure of health at all.
The idea that there is an “ideal bmi” is called into question by the fact that in 1998 the “ideal/healthy BMI” was changed. Three members of the committee responsible for making the recommendation had direct ties to pharmaceuticals that manufactured diet pills for profit. A fourth member was the lead scientist for the program advisory committee of Weight Watchers International. This committee advocated dieting for everyone who had a BMI more than 24. They shaved 15-20 lbs off the definition of “ideal/healthy weight” which made about 29 million Americans “overweight, ” and thus “unhealthy,” overnight. It also gave those making the recommendations 29 million new potential clients. Now there is talk of lowering the BMI again. So it’s difficult to defend the idea that, even if there was an “ideal height/weight ratio”, we have any idea what it is.
Beyond that, the research linking a higher BMI with diseases is correlational, meaning that they happen at the same time. That doesn’t mean that you can assume that BMI causes the diseases or that you can assume that decreasing BMI will cure or prevent those diseases. Often in August the most ice cream is eaten and the most murders take place, but we can’t assume that taking ice cream off the shelves will decrease the murder rate. Correlation never implies causation because it’s possible that the two things are unrelated or that a third thing causes both issues (in this case maybe heat increases the propensity for murder and the chances that people eat ice cream?)
People often ask me how I can “ignore” all of the correlational evidence that having a high BMI is unhealthy. I’m not ignoring it, I’m simply putting it to the scientific rigor that it deserves. It turns out that the same diseases that are correlated with high BMI are also correlated with being under a high degree of stress over a long period of time. Like, perhaps, the stress of living in a society where the government wages war on you for the way you look? Either way, this issue is absolutely not as cut and dried as we are lead to believe.
The use of BMI is cheap, lazy, bad medicine. We don’t need BMI to be a middleman between us and our health, because we can measure metabolic health, we can measure strength, stamina, and flexibility and we can work on those things if we want to without trying to change our body size or shape.
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