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Thursday, 31 May 2012

Discrimination, tall people and BMI

Not that I am obsessed with BMI or anything.  I was delighted to read in the Reflections on Body Image report out yesterday, that BMI is under review by the Department of Health as an "indicator of health".  It is not and never was and shall never be a measure of physical or mental health and should never be used as a diagnostic tool on its own.

It was a tool refined by Louis I Dublin as a measure of mortality rate statistics for use by the Metropolitan Life Insurance Company to calculate rates for life insurance.  It is presently used by insurance companies worldwide as an exclusion criteria for many health conditions and, in some cases, exclusion from any medical coverage at all.  This means that Soane Tonga'uiha, the loose-head prop for the Northampton Saints, would be unable to get coverage in the USA, as his BMI is 34.7

Soane Tonga'uiha Soane Tongauiha of Northampton charges at Anthony Forest of Bourgoin during the European Challenge Cup Final between Northampton and Bourgoin at The Stoop on May 22, 2009 in London, England.  (Photo by Mike Hewitt/Getty Images) *** Local Caption *** Soane Tongauiha;Anthony Forest

Not that I am going to tell him..............

Imagine my delight when Extralongtail told me today that as BMI is an areal rather than volumetric measure, it discriminates against tall people.  I did ask her to explain further but she informs me that she needs to go out for a sustaining lunch before attempting to explain this:

 m = \int_V \rho(\mathbf{r})\,dV.


  1. I know. Ridiculous. Which is the point I always tried to make to our treatment team about why my former rugby playing No3 forward son should have a BMI of higher than the 20 he is currently at. I can't wait to tell him that BMIs may be binned.

  2. Rod McClymont01 June, 2012

    BMIs and rugby players (or similar) boys recovering from anorexia are interesting! I have looked after a few now who were extreme low BMI- very low body fat and muscle mass when first presenting, with re-feeding followed the 'normal' pattern initially with BMI and body fat increasing in a linear fashion but then, after they were weight restored (growing, cogitively recovered)and where getting back into rugby ( or in 1 weight lifting), BMI kept progressing whilst body fat decreased- they developed high muscle/lean mass, had BMIs that were 'over-weight'(>85th centile or even >95th centile) if looked at in isolation but very normal body fat mass (40th - 60th centile). plotting a graph with BMI and % fat mass (from skin folds, bioimpedance and a few DEXA scans along the way)showed this progressive increase in BMI till a plateau at a 'high' level as fat mass showed a inverted 'U' curve increasing from very low to moderately elevated (early recovery before muscle mass restored)then going down again to plateau at average levels.