Thursday, June 14, 2012

Should the BMI Be Adjusted for Microbiome Mass?

As attention to obesity in this country heats up, and let's bear in mind nearly 12 million citizens have been added to the rolls of the "obese" since the BMI or "body mass index" has been adopted (thereby assuring much more $$$$ for treatments, therapies etc. as imposed by medical practitioners) - one must wonder whether this measure is truly accurate.

Again, to remind readers, BMI is computed thus:

BMI = Wt (lbs.)/  [ht (in)]^2  x 703

The BMI categories which follow from this are designated:

• Underweight = <18.5
• Normal weight = 18.5–24.9

• Overweight = 25–29.9

• Obesity = BMI of 30 or greater

A BMI calculator that can do the computations quickly is at:
Now, in my case, given my current weight is 188 lbs. and my height is 5' 6", the calculator shows my BMI = 30.3 or just over the threshold for obese. But is this really an accurate representation? According to the initial findings of the Human MicroBiome Project (a sister to the Human Genome Project) a typical human carries about ten bacterial cells for every human cell.  These 'flora' ride along and are always working - whether to aid in digestion(say in the gut) or to fend off the bacterial bad nasties that are always striving to acquire control - such as clostridium difficilie or 'c. diff.' in the gut - which can occur if a person takes too strong an antibiotic and kills off too many of the beneficial bugs (that neutralize the c. diff.).
According to the $173 million project funded by the National Institutes of Health, we each have up to ten trillion bacteria on us and they are not merely passive 'passengers' along for the ride, but 'metabolically active'. We need to see them in the same light as any natural ecosystem, which means if it gets out of balance bad things can occur - whether c. diff. or irritable bowel syndrome, or psoriasis. We need these guys to keep the bad nasties in check, in other words.
But here's the deal: given the microbes make up anywhere from 1 to 3 percent of a human's body mass, with the higher percentages going to higher weights (e.g. 3 % is applicable to a person in the 188- 200 lb. wt. class) then that means a 200 lb. person can harbor as much as 6 lbs. of bacteria, according to Dr. Eric Greene, Director of NIH's Human Genome Research Institute.
Now, if this is so, then it means that the BMI surely has to be adjusted in order to isolate one's pure (human) body mass from the mass of the non-human organisms ( 'bacteria'). Thus, in my case, if I am carrying about 6 lbs. of these denizens then one would need to correct via subtraction:
e.g. Wt.' = Wt. - 6 lbs. = 188 lbs. - 6 lbs. = 182 lbs.
And re-calculating the BMI once more (minus the extras) yields:
BMI =  Wt'  (lbs.)/ [ht (in)] ^2 x 703  =  182 lbs./ (66 in.)^2 x 703
or from the calculator:
BMI = 29.4
In other words, I instantly transfer from the "obese" category to the simply "overweight. What a difference that such an adjustment can make in the right circumstances!
Will the health-medical complex and cognoscenti accept this correction? Likely as not they won't. They will simply argue that the BMI "already accommodates" the bacterial colonies since every human has them- so no need for special adjustment. However, I will stand by my adjusted version! Reason: If the mass of the bacterial bugs constitutes an additional contribution that doesn't specifically belong to me, why include them? Especially if it means the difference between being merely "overweight" and "obese"?

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