BMI, again

Yes, it’s a pet peeve.

This is a comment from over at Instapundit, figured I’d copy-paste it so that it has a chance of being read.

***************

Found the article.

https://jamanetwork.com/journals/jamapediatrics/article-abstract/2685908

Those who looked at the years and went “hm, first one is before the BMI change, second is after,” yes they used BMI studies for each span.

On the upside, they did at least pick a cohort that has almost entirely hit puberty, 16-19.

On the other hand, they were using a screening test to diagnose “overweight.”

It’s known bad:

To find out whether BMI correlated with actual markers of health, a team of UCLA researchers analyzed data from 40,420 individuals who participated in the 2005-2012 National Health and Nutrition Examination Survey. They looked at individuals’ blood pressure, triglycerides, cholesterol, glucose, insulin resistance and C-reactive protein data — markers that are linked to heart disease and inflammation, among other issues.

They found that nearly half (47.4%) of overweight people and 29% of obese people were, from a metabolic standpoint, quite healthy. On the flip side, more than 30% of individuals with “normal” weights were metabolically unhealthy.

http://www.latimes.com/science/sciencenow/la-sci-sn-bmi-does-not-measure-health-20160204-story.html

And “overweight” isn’t significantly associated with bad health outcomes– the ‘risk’ there is that you MIGHT be headed to “obese.” The lowest health risk appears to be situated inside of “overweight.”
http://circ.ahajournals.org/content/119/25/3263

Which makes sense for a screening test– having more body fat improves the outcomes if you get sick, but you don’t want so much body fat that it makes you sick, so logically the healthiest folks would be inside of the false positive.

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6 thoughts on “BMI, again”

  1. BMI is such a poor choice for determining health. Just about any athlete that spends a significant amount of time hitting the weights is gonna show up overweight and obese ranges. Mark McGwire coming out of college in ’84 would have rated “overweight” on the BMI chart. By the time he broke Maris’ home run record he would have been considered “obese”.

    Lawrence Taylor would have been considered “obese” during his playing career

    1. I’ve only not been over-weight once in my life– and my body fat was low enough that it shut down my female cycle, but I didn’t even recognize that was why it had happened because I “knew” I was barely in a healthy weight zone.

      I’m too heavy right now, not counting pregnancy, but maybe ten – fifteen pounds. Was at a healthy weight without dietary scewballery after I tried a B complex and the extra weight melted off.

      1. coming out of high school I had a BMI of 20, low end of normal. A few years later I had to put on muscle for my job, and had a BMI of 24, high end of normal. Now I’m around 32, after being as high as 35. I’d like to get down to about 29 again. I think that’s doable. But it’s still borderline obese.

      2. A measurement that’s as likely to be wrong about “obese” people being unhealthy due to weight as it is about “normal” people being unhealthy due to weight is seriously screwy. :(

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