Even More Evidence BMI Isn't A Good Measure Of Health

We already knew BMI isn't a great measure of whether a person is fat or not, but now a study confirms that it's not a good measure of health either.

Photo by Andy Melton.

BMI, or Body Mass Index, is popular because it's simple to measure. If you've ever read a headline about research on "obesity", they're almost never referring to how much fat was on research subjects' bodies: it's all about BMI.

It's true that fatter people usually have a higher BMI and that people with higher BMI are more likely to have more insulin resistance, higher blood pressure, and other risk factors for heart disease and metabolic disorders.

But when researchers from UCLA compared the BMI of over 40,000 people to their blood pressure, triglycerides, cholesterol, blood glucose, insulin resistance and C-reactive protein levels, they found that BMI didn't match up with these health measures as often as you'd think.

Half of people in the "overweight" category (BMI 25-29) passed these tests with flying colours. Meanwhile, 30 per cent of people with a normal BMI scored as unhealthy.

So if you're skinny, that doesn't mean you're off the hook; and if you're fat, you might very well still be healthy. The researcher who ran the study, A. Janet Tomiyama, told Medical News Today that it's unfair that employer wellness programs can charge more to people with high BMIs, saying that "employers, policy makers and insurance companies should focus on actual health markers".

Misclassification of cardiometabolic health when using body mass index categories in NHANES 2005 -- 2012 [International Journal of Obesity via Medical News Today]


    It still also ignores the fact that muscle is denser than fat.

      And many more assumptions or misconceptions, such as:

      1. ignoring the cube-square rule
      2, not accounting for variations in muscle bulk, bone density, skeletal mass, etc
      3. having never been validated against body fat %age
      4. being based on associations with no definite causal link to ill health established

      This isn't the first paper to seriously question the validity of BMI. But sadly it's unlikely to go away any time soon. Mainly since it's so easy to calculate, whereas more robust anthropomorphic measures require time and equipment.

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