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Polymerase chain reaction is a cornerstone of molecular biology research. Using short pieces of single-stranded DNA called primers the previously invisible becomes tangible.

Monday, April 25, 2005

A Misconception is Born

Disclaimer: The following post discusses scientific and medical issues. I am neither an MD nor a PhD. Consult a physician for medical advice. Talk to a PhD, read a text or check a peer-reviewed journal if you have science questions. I’ve included at the bottom of this post links to medical doctors who have covered this topic. I’m writing because I can’t sleep and I’ve been annoyed by the news, though the two are not necessarily related. I may remove this disclaimer in the future if I post a separate more standard one covering this whole blog.

NY Yankee, Alex Rodriguez
NY resident, Primer

According to federal guidelines to determine body mass index (BMI), Alex Rodriguez and I have something in common. We are both overweight. The kicker, I’m less overweight than A-Rod. This explains why I’m LMAO in the image above. It also underscores the limitations of a recent study published in the Journal of the American Medical Association, Excess Deaths Associated With Underweight, Overweight, and Obesity.

Flegal, Graubard, Williamson and Gail, the authors of this study, aimed to improve the metrics of correlating weight status to mortality rates. Previous studies, the authors stated, incompletely accounted for confounding factors like smoking and age variation and did not include estimation of error or uncertainty.

The authors reported the statistical methods and computer programs used to address the shortcomings of the previous studies. Their results indicate the previous studies overestimated the number of deaths associated with all weights considered non-normal. It is unsurprising this study’s numbers differ from those of previous studies. Flegal, et al used different calculations, considered additional variables and differentially grouped data. One would be more surprised if the numbers turned out to be the same.

Of particular interest to the mainstream media was the apparent lower rate of mortality associated with overweight compared to underweight. Look at these articles and witness the birth of a misconception:

What’s the take home message being pushed by the media? “You’re not only ok being overweight, you’ll probably live longer.” Problem is, that’s just plain wrong.

Brooks’ op-ed is particularly misleading.

“The release of a report in The Journal of the American Medical Association indicating that overweight people actually live longer than normal-weight people represents an important moment in the history of world civilization.”

“…health-conscious people can hit a point of negative returns, so the more fit they are, the quicker they kick the bucket. People who work out, eat responsibly and deserve to live are more likely to be culled by the Thin Reaper.”

Yeah, it would be an important moment, that is, if it were true. The authors note that the lower mortality rate associated with overweight compared to normal-weight may just as likely be attributable to limitations of their model. Their calculation of BMI, though accepted practice, is questionable. Currently only height and weight are used to determine BMI. Physical activity, waistline measurement, percent body fat, muscle development, gender, none of this is factored into determining BMI. It’s that dubious nature of BMI that would classify former Major League Baseball MVP, Alex Rodriguez, as being more overweight than I am. Those that know me can appreciate the absurdity of that claim. The authors also note that, “it would be of interest,” to see how the numbers change if they were to consider only mortality due to obesity-linked causes like cardiovascular disease. And finally, the authors state that they did not take into account the advances in medication and treatment of cardiovascular disease risks. No one disputes the rise in obesity is directly proportional to the increase in lipid-lowering and anti-hypertensive medication prescriptions.

So, what we have here is a study that is more statistically rigorous and precise than previous studies. It remains to be determined, however, if it accurately describes and can predict the public health condition.

Some thoughts:

  • A more inclusive method to determine BMI should be developed to greater reflect and more accurately describe the diversity of body types.
  • A study incorporating the more inclusive BMI and restricting mortality data to obesity-linked causes should be conducted.
  • We should also be looking at the relationship between weight status and disability or disease rather than total mortality rate.
  • The effect of treatment and medication advances should be considered.
  • This study should not be considered a license for sloth and gluttony.


The photograph of Alex Rodriguez was copied from SportsFrog. The image was then resized to 55%. There was no alteration of body proportion. The image is a faithful representation of Alex Rodriguez.

The Primer avatar was created at South Park Studio v2.0. The screenshot was converted to jpeg and resized to 68%. Although the image is a cartoon, by many accounts it is a fairly accurate representation of Primer. Okay, my head is slightly pointier.

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