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DLR's avatar

I think part of the problem is a poorly chosen interval for 'normal' BMI. Here's a study that looked at all cause mortality for BMI ranges within the 'normal' BMI range. Along with the usual suspects they compared BMIs of 18.5-20; 20-22.5; 22.5-25; 25·0–27·5 ;

All cause mortality was

1.13 for 18.5-20 'Normal'

1.00 for 20-22.5 'Normal'

1.00 for 22.5-25 'Normal'

1.07 for 25-27.5

The 'Normal' BMI range 18.5-20 is obviously less healthy than the two BMI ranges of 20-22.5 and 22.5-25. It dragging down the average!

18.5-20 should be redefined to underweight, and 'Normal BMI' should be redefined to be 20-25.

I mean, just take a look at it-- it is more unhealthy to be in the 'Normal' BMI range 18.5-20 than it is to be in the 'Overweight' BMI range 25-27.5

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4995441/

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Matt's avatar

The reason BMI is not an effective measure is because it doesn’t differentiate between lean muscle and body fat. It is effective for sedentary individuals because it cannot account for muscular development. A better measure would be body fat percentage as there are huge differences in health outcomes between somebody with a BMI of 28 and 40% body fat and somebody with a BMI of 28 and 10% body fat. Generally the leaner individual will have substantially better health outcomes. Then the counterfactual becomes bodybuilders who have very high BMI’s, very low body fat, but typically a lot of physical damage and health risks associated with the substances they’ve used to enhance their muscular development.

There unfortunately is no perfect measure for all of society due to all the nuances involved.

I do wonder if some sort of calculation could be developed that combines BMI with sometime like A1C which can differentiate between unhealthy “overweight and obese” BMI’s and healthy ones.

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