From Your Health Journal…..”I just love Forbes.com, and recommend it to all of you. So many people think of it just as a business site, but they run many great health articles like the one being reviewed today. Forbes is reporting about the controversy of the BMI or Body Mass Index – which is an indicator if someone’s weight falls within a healthy range. It is a chart that takes height and weight measurements – which correspond to a number. For example, if someone’s BMI is below 18, they may be considered underweight. Around 18-25 is considered normal, 25-30 overweight, and above 30 is considered obese. The BMI has stirred controversy over the years, as some experts like it, others not. However, like IQ, the single number for BMI does not tell us all we need to know. This is because BMI does not distinguish between fat mass and lean mass (muscle, water, bone, etc). Someone who is physically fit can have a high BMI due to having greater than average muscle mass. While misclassifying some people as obese (BMI of 30 or greater) who are not obese, using this criterion actually misses more than half of people with excess body fat. Please visit the Forbes.com web site (link provided below) to read the full story.”
From the article…..
We all want simple and clear answers telling us how to improve our health, but no one number – in this case, body mass index – and no one study can provide the final word.
Last week’s paper in JAMA on body mass index and mortality may have set a record for creating confusion in the public at large and generating a bewildering range of responses among experts – some of them startling in their uncritical acceptance, others in their hostility.
At one extreme, Walter Willett, professor of nutrition and epidemiology at Harvard, denounced the paper, calling it a “pile of rubbish” and saying that “no one should waste their time reading it.” He emphasized that, “We have a huge amount of other literature showing that people who gain weight or are overweight have increased risk of diabetes, heart disease, stroke, many cancers and many other conditions.”
At the other extreme, Paul Campos, a professor of law and author of “The Obesity Myth,” in a New York Times op-ed, leveled attacked the public health establishment for classifying two-thirds of the adult U.S. population as being in need of weight reduction.
How could a dry, scholarly paper have opened up such a Pandora’s box, and how could interpretations of it differ so drastically?
Part of the problem is that the latest paper tends to get highlighted in the public sphere in a way that makes it seem like the final word, as if it supercedes all prior knowledge and delivers revealed truth. Few papers can live up to this kind of billing. This “microscope effect” focuses attention on one study to the exclusion of other considerations. Let’s look at what the study actually entails.
The paper by Katherine Flegal and colleagues presents the results of a meta-analysis – that is, an arithmetic averaging — of the results of studies worldwide that examined the association of body mass index (BMI) with subsequent death from any cause. The sample included 97 studies, nearly 3 million people, and 270,000 deaths. The authors used standard categories of BMI: 18.5-<25 (normal weight), 25-<30 (overweight), and >=30 (obese). The last category was further subdivided into 30-<35 (class 1), 35-<40 (class 2), and >=40 (class 3).
What they found is that, compared to normal weight individuals, those in the overweight category had a lower risk of dying of any cause, and those in the obese category had an elevated risk. However, more than half of those in the obese category were in class 1, and these individuals had no increased risk of dying compared to normal weight individuals. Class 2 and 3 individuals did have a significantly elevated risk of death.
Thus, this analysis correlating BMI with risk of dying found that being overweight actually appeared beneficial and that the ill effects of obesity were limited to the very obese.
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