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Another CDC Blunder

April 28, 2005 09:52 AM

The CDC has corrected its earlier claims that obesity is the number 2 killer in the US. No one who knows anything about epidemiology and its dismal state believed this claim, though plenty of do-gooders who want to tell you what to do made much of it.

It has long been known that body mass is a predictor of mortality, but insufficiently recognized that rapid loss of body mass is part of the dying process. If you lose 40% of your body mass, you are dead, whether the underlying condition is sepsis, AIDs, cancer, etc. The aged simply die on a longer time scale, over the course of an adult life and they do so as, eventually, their body mass falls to the 40% point. Basically, one dies as body mass declines to the critical point and this is not a matter of age, but of the ability to sustain a system far from equilibrium.

Mass is the measure of how efficiently you maintain your non-equilibrium, thermodynamic state as you take in from and expel energy to the environment. So, what some call the "effect" of mass on mortality is really a complex dynamic interplay of mass and mortality. Among older individuals, body mass is associated with increased longevity. But, it is non-linear; above a certain point the curve turns downward. The same thing can be said on the downside; lower mass improves longevity (particularly among rats), but further loss of mass is associated with higher mortality.

How could it be otherwise? Humans evolved under a strong set of environmental and physiological constraints and, thus, there is an optimal body size. Extremely tall people do not live as long as others; their circulatory system is under stress from maintaining a high blood column and there is a scaling effect from the high mass on the vascular and pulmonary systems. Undersized infants do not fare well and some become insulin resistant in the womb in the competition for the mother's scarce nutritional resources. Paradoxically, such infants usually battle obesity later in life, a major problem among the insulin-resistant.

Epidemiology is not a science, it is statistical alchemy, creating epidemics where there are none. You make your career in the field by finding (meaning: statistically torturing the data to find) a "problem." The media are happy to announce and even exaggerate the results before they are peer reviewed and to ignore later retractions or corrections. This latest correction just happened to get some publicity; one can go back over recent announcements and find contradiction after contradiction (wine is good for you, wine is bad for you).

G. Le Fanu, a British physician and medical writer, has a really fine book, The Rise and Fall of Modern Medicine, that calls for the dissolution of departments of epidemiology, who have strayed far from the foundations of the field. I agree.

· Evolutionary Fitness

Comments

Posted by: Flower Online [TypeKey Profile Page] at September 11, 2006 12:58 PM

dear art
great post on body mass and mortality.I've had
an intuitive grasp on the concept but you helped to make it more clear.
my question is what to do think of calorie restriction people?I myself have always had a problem with it although I find what they say very interesting.
sincerely
barry bocchieri

Posted by: barry bocchieri at April 29, 2005 8:34 AM

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