Holding Hands Together Forever

BMI: Can’t Let It Go

BMI (body mass index) is a tool that everybody loves to hate. And despite all the problems we have with it and plenty of other options, we can’t seem to let it go. That’s the conclusion that Steven Heymfield and Scott Going presented to an auditorium packed with dietitians at the annual meeting of the Academy of Nutrition and Dietetics — FNCE 2014.

Practice Applications of BMIHeymsfield reviewed the scientific basis for BMI. He started with the consensus that BMI is a good tool for predicting health risk at the extremes at values below 18.5 and above 30. He went on to review its limitations and a variety of the so-called BMI paradoxes — special populations where high BMI seems to predict less, not more, mortality risk.

He also discussed the value of waist circumference and presented three alternative indices that might provide more insight, but need more work:

  • Body Adiposity Index
  • Body Roundness Index
  • A Body Shape Index (ABSI)

Body Roundness index was found in a new assessment to be a pretty good indicator of cardiovascular health status. The assessment was just published in PLOS ONE.

Going added an overview of methods for more directly measuring adiposity and body composition, along with some practical insight on their application. The methods he covered were:

  • Densitometry
  • Dual Energy X-Ray Absorptiometry (DXA)
  • Bioelectrical Impedance Analysis (BIA)
  • Anthropometry (relatively simple physical measures)

After all is said and done, people can’t seem to call it quits with BMI. It gets people into trouble when they forget it’s just a surrogate for adiposity. It’s not the definition of obesity — it’s just a first-pass screening tool. It’s useful for that purpose and nothing more.

Click here for Heymesfield’s slides, here for Going’s outline and references, and  here for the new study of Body Roundness Index as compared to BMI, waist circumference, and ABSI.

Holding Hands Together Forever, photograph © Martin Fisch / flickr

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2 Responses to “BMI: Can’t Let It Go”

  1. October 20, 2014 at 6:23 am, Susan Kennedy said:

    What measures do you recommend in the school setting for children and adolescents

    • October 20, 2014 at 7:49 pm, Ted said:

      I have strong reservations about BMI screening at school. Evaluation of health risks should be done by pediatricians, not schools, because schools are not equipped to treat childhood obesity and related health conditions.

      Schools should stick to their knitting. They need to worry more about weight-based bullying and shaming. They should pay attention to providing good nutrition and physical activity at school. Offering up unsolicited advice about body weight is not a help.

      I wrote more about this back in May at https://conscienhealth.org/2014/05/should-schools-send-fat-letters-home/