Way back in 1998 I became overweight in just one day. It wasn't because I had gone on a binge of eating and drinking. Rather it was because a committee convened by the National Heart Institute redefined overweight to be a body mass index (BMI) of 25 or more for both men and women. Body mass index is calculated by dividing a person's weight in kilograms by the square of the person's height in meters. If you prefer to use English units, its your weight in pounds divided by the square of your height in inches, then multiplied by 703.
I had a BMI of 25.8, so I was now overweight. Before 1998, a man was officially overweight with a BMI of 27.8 and a woman at 27.3, but then the rules were changed.
BMI doesn't scale well. A tall man with the exact same build and body composition as a shorter man will have a higher BMI. Secondly, the measure ignores variation in body shapes. Some people are slender; others are stocky. Moreover, people carry fat in different places. Subcutaneous fat just below the skin is generally not associated with a steep rise in mortality, while abdominal fat is. Finally, BMI does not differentiate between fat and muscle mass. This glaring drawback means that many muscular athletes are considered overweight, or even obese. (1)
Paul Campos calculeted in 2004 that 66 of the NFL's kickers—traditionally the position reserved for pencil necked players—were overweight. I doubt you would think of Hollywood stars such as Richard Gere, Pierce Brosnan and Kevin Costner as being overweight or borderline obese, yet with their respective BMI's of 26.8, 27.1 and 29.2, Gere and Brosnan were overweight and Costner borderline obese. (Note- Campos's book was published in 2004, so these numbers could be different for these movie starts today). (2)
Glenn Gaesser of the University of Virginia pointed out in his book in 2002 that studies had consistently failed to find any correlation between increasing BMI and higher mortality in people 65 and over and 78% of the approximately 2.3 million annual deaths in the United States occur among people who are at lest sixty-five. Thus, 78% of all deaths lack even the beginning of a statistical link with BMI. (3)
A study conducted in Norway in the mid-1980s followed 1.8 million people for 10 years. The highest life expectancy (79.7 years) was found among people with BMI figures between 26 and 28, all of whom were overweight according to current US government guidelines. The lowest life expectancy (74.2 years) was found among those with BMI figures below 18. Those with BMI figures between 18 and 20—most of whom were at what our public health authorities claim is an optimal weight—had a lower life expectancy than those with BMI figures between 34 and 36; people who according to those same authorities were roughly 60 to 75 pounds overweight and, therefore, seriously obese. (2)
Another study looked at 2.9 million people. Those classified as overweight, which are those with a BMI greater than or equal to 25 and less than 30, had a 6% lower chance of dying than those with a BMI greater than or equal to 18.5 and less than 25, considered the normal range. (4)
One could go on and on listing studies that show the problems with BMI. The most recent are results from a UC Santa Barbara and UCLA team that Julie Cohen says 'could be the death knell for BMI.' (5)
This research reveals that millions of American labeled overweight or obese based on their BMI are, in fact, 'perfectly healthy.' The findings suggest that 34.4 million American considered overweight by virtue of BMI are actually healthy, as are 19.8 million who are considered obese.
According to co-author Jeffrey Hunger of UCSB, BMI is a deeply flawed measure of health. “In the overweight category, 47 percent are perfectly healthy,” he said. “So to be using BMI as a health proxy—particularly for everyone within that category—is simply incorrect. Our study should be the final nail in the coffin for BMI.” (6)
Using data from the most recent National Health and Nutrition Examination Survey, the scientists analyzed blood pressure, blood sugar and cholesterol. The results showed that more than 2 million people identified as 'very obese' by virtue of having a BMI of 35 or higher are, in reality, healthy. That's about 15 percent of Americans so classified. The research also revealed that more than 30 percent of those with BMI's in the 'normal range'--about 20.7 million people—are actually unhealthy based on their other markers.
“Not only does BMI mislabel 54 million individuals as unhealthy, it actually overlooks a large group of individuals considered to have a 'healthy' BMI who are actually unhealthy when you look at underlying clinical indicators,” said Hunger. “We used a fairly strict definition of health. You had to be at clinically healthy levels on four out of the five health indicators assessed.” (6)
The evidence about the problems with BMI is overwhelming and has been reported for many years. The fact that this most recent study has been labeled a 'death knell' simply adds more credence to the fallacy of this measurement technique.
Jack Dini
Livermore, CA
References
1. Ross Pomeroy, “A new potential replacement for body mass index,” realclearscience.com, December 30, 2015
2. Paul Campos, The Obesity Myth, (New York, Gotham Books, 2004)
3. Glenn Gaesser, Big Fat Lies: The Truth About Your Weight and Your Health, (Carlsbad, CA, Gurze Books, 2002)
4. Carl Bialik, “A good way to measure obesity? Fat chance!”, online.wsj.com, January 12, 2013
5. Julie Cohen, “BMI is not an accurate measure of health according to research by UCSB psychologist Jeffrey hunger and colleagues,” news.ucsb, February 4, 2016
6. A. Janet Tomiyama et al., “Misclassification of cardiometabolic health when using body mass index categories in NHANES 2005-2012”
