The Attack on Obesity and the BMI Myth

The Attack on Obesity and the BMI Myth

The obesity epidemic makes headlines daily as newscasters recite statistics about the dangers of excess body weight. Mexican food, movie popcorn and the all-American burger have all fallen under the disapproving glare of public health proponents. Experts inveigh against the dangers of carrying extra flab and warn that without drastic measures, the current generation of overweight kids will become the first generation to lead shorter lives than their parents. All too often, this hatred of fat transfers itself to a hatred of fat people.

With so many terrifying statistics about heart disease, type 2 diabetes, stroke and organ dysfunction related to obesity, it’s easy to conclude that any excess weight imperils people who carry it. To some extent, the concerns are justified; these risks are real at the highest ends of the weight spectrum. There’s little question that significant excess weight contributes to serious health problems. Extreme obesity can also impede quality of life as well as its quantity.

However, the foundation on which the notion of obesity rests — body mass index, or BMI — is fundamentally flawed. Without a clear vision of what constitutes overweight and obesity, it’s impossible to assert that any amount of excess weight is bad. On the contrary, studies of the health consequences of significantly low body weight reveal that too little weight is as lethal as extreme obesity and considerably more dangerous than having a moderately high BMI. These statistics also look less alarming under more careful scrutiny, as many studies fail to differentiate between a few extra pounds and a few hundred of them.

The Myth of BMI

In 1850, doctors had no antibiotics, nor did medical personnel have a germ theory of disease to explain why illnesses happened. Doctors who washed their hands between patients drew scorn from colleagues for their fastidiousness. Surgery without anesthetics or blood typing was frequently fatal. It was also the year that the Body Mass Index, or BMI, came into being. Unlike other outdated medical practices, BMI still remains in use.

The calculations for BMI involve only height and weight. Measuring the relationship between these two characteristics against a set of ideal characteristics theoretically gives an idea of an individual’s overall health. For people with moderate muscle mass, this relationship can indicate overweight or obesity. However, because BMI fails to take gender, age, fitness or body composition into account, millions of healthy people wind up in the “overweight” or “obese” categories.

At the extremes of physical fitness, BMI is not only inaccurate, it’s absurd. Many professional athletes are overweight or obese according to BMI figures. NFL quarterback Tom Brady falls in the middle of the overweight category with a BMI of 27.5, while his shorter counterpart Drew Brees edges dangerously close to obesity with a BMI of 28.5. Tony Romo has even less wiggle room with his BMI of 29. One more point and he’d be obese like Arnold Schwarzenegger who had a BMI of 32.1 — well into the obese category — when he won his Mr. Universe title.

The Risks of Being Underweight

At the opposite end of the weight spectrum are those whose BMI numbers fall below 18.5. People with lower body weights face a higher risk of osteoporosis, infertility, a weakened immune system and less resilience, according to England’s National Health Service website. Studies of underweight people suggest that having low body weight carries a risk of death only slightly smaller than the mortality figures for severely obese individuals.

The Journal of the American Medical Association published a comprehensive look at excess death rates for a spectrum of BMI numbers. When they compared the figures for obese, overweight and underweight categories against those of normal BMI, between 18.5 and 25, researchers found more excess deaths in the obese category than any other. However, the underweight group also had a larger death rate compared to those of the normal and overweight BMI groups. These statistics look even more alarming for underweight people when morbidly obese people are separated from the mildly obese cohort.

The findings from the medical journal Obesity are even more stark. Researchers from Canada and the U.S. worked jointly to study BMI and death rates and concluded plainly that “obesity class I was not associated with an increased risk of mortality.” In other words, not only were overweight people on par with those of average BMI, but mildly obese people also suffered no apparent ill effects.

If BMI isn’t a valid tool for determining obesity, what is? One answer might be measuring the waist-to-hip ratio. Investigators at the University of Texas Southwestern Medical Center found that this ratio might have greater predictive value for obesity-related health risks than BMI. Other methods focus on measuring actual body fat percentage; hydrostatic analysis or skin-fold thickness measurements determine body composition.

One of the most effective tools is honest self-assessment. A full-length mirror speaks volumes of wisdom that no BMI graph can impart.

Redefining Obesity

Being underweight carries almost as many serious health risks as severe obesity, yet bears none of the stigma. Thinness is enviable; obesity is a character flaw. Despite the fact that carrying a few extra pounds is healthier than being underweight by a similar amount, the prevailing attitude is that no fat is good fat. The tool that medical professionals used as a yardstick has become an instrument of punishment for heavy people.

More realistic appraisals of the risks of excess fat are leading to changes within the medical establishment. While health care professionals’ views are evolving on overweight and mild obesity, the public face of obesity is slower to change. Media outlets still focus on the obesity epidemic and its potential costs, unfairly stigmatizing any weight gain as a public health issue instead of a personal choice.

When strident warnings about the evils of butter or brownies grow too deafening, it’s helpful to think of the state of medicine in 1850 and recall how times have changed. Eventually the world will catch up with modern medicine.

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