The Skinny on Size Zero and the Real Dangers of BMI

Ever since 98-pound Uruguayan model Luisel Ramos dropped dead at an August fashion show, critics around the world have been calling for an end to the uber-thin trend in catwalkers. So far it has worked – kind of. The media fallout over Ramos – who at 5’9” had a body mass index (BMI) of just 14.5 – resulted in fashion-week organizers in New York, Milan and Madrid banning girls with BMIs below the World Health Organization’s lowest “normal” score of 18.5. Yet even as headlines fuss over bids to ban size-zero models, advertisements continue to idolize them.

There are two separate problems in displaying inordinately thin women as the embodiment of beauty. One, the fashion industry may implicitly encourage models to starve, take drugs and die in order to fit into the going designer’s sample size. And two, the constant media parade of impossibly svelte women may batter the psyches and eating habits of the rest of the normal world. U.K. Culture Secretary Tessa Jowell summed up this sentiment best: “This is not simply about the fashion industry and ensuring that girls are not exploited. There are also wider social consequences like the impact of the culture of thinness on the well-being and aspirations of teenage girls.”

Invoking BMI, unfortunately, won’t help solve either problem. It is an imperfect tool that may fail to gauge a model’s overall health and therefore fail to protect her. What’s more, a BMI cutoff is unlikely to stem societal messages to vulnerable young women, especially those who are genetically at risk for eating disorders like anorexia and bulimia. While it’s clear that the media play a significant role in cultural body attitudes, which can serve as a trigger for food-related mental illness, anorexia and bulimia are still poorly understood. Pointing the finger at the size zeros or sub 18.5-ers is missing the point.

The body mass index was developed by Belgian statistician Adolphe Quetelet in the mid-1800s. It models human beings mathematically, like perfect cylinders: weight (in kilograms) divided by height (in meters) squared. In the 1980s, as doctors caught the first glimpses of the obesity crisis to come, BMI took over from height and weight tables as the primary measure of a healthy body. Today, organizations like the U.S. Centers for Disease Control and the World Health Organization have divided BMI into four categories: under 18.5 is underweight; 18.5 to 24.9 is normal; 25 to 29.9 is overweight and over 30 is obese. There has been, for years, a debate over where the lowest “normal” BMI lies. It used to be 20, but some say it’s 19. Fifteen is definitely bad, and under 17.5 is part of the accepted diagnosis for anorexia. 

The truth is that BMI, though useful for big epidemiological studies, is a pretty blunt instrument. The formula is the same for men and women, even though men of the same height, on average, weigh more than their female counterparts. A study from the March issue of Medicine & Science in Sports & Exercise found that BMI was a poor determinant of body fat in male and female college students, and especially bad at gauging health for athletes due to all that excess muscle they carry. The authors suggested alternative “healthy” BMI ranges specifically tailored for nonathlete men and women, and their sportier friends.

Though BMI was developed to approximate “fatness,” you can still score in the healthy range while carrying an excess of belly fat (according to some studies bellies are an even better predictor of heart disease and diabetes risk). Very short people are also often misdiagnosed as “healthy” when they have a worrying level of body fat. A 2003 study comparing short-statured and taller people with the same BMI concluded that, for short people, obesity should sit at a cut-off of 25 instead of 30. That’s a big difference. Similar distortions likely occur at the other extreme of the height-weight scale, where we find our female models.

So a perfectly healthy model who actually eats and one who subsists on Diet Coke, cigarettes and cocaine could well have the same BMI. Young, active girls blessed with a certain metabolism and bone structure may have a BMI of 18 (or very slightly under) and be in no particular danger. So based on the science, healthy but sub-18.5 models may be justified in suing for discrimination, as they threatened to do in February if the London Fashion Week chose the 18.5 cutoff. Perhaps everyone could be happy with mid-upper arm circumference, which the U.N. Committee on Nutrition considers to be a better indicator of starvation and muscle atrophy? It is independent of height, quick to measure and much easier, prior to the runway, than a full body-fat x-ray or a stomach-contents analysis.

Healthily thin or truly drop dead gorgeous: the question remains as to whether very thin models hurt the public at large. A study published just last month from the University of Missouri found that looking at models in magazine ads made women of all shapes, sizes and body esteem feel bad about themselves. Over the past two decades multitudes of studies have unearthed similar findings: In experimental settings, looking at thin models makes women feel bad, angry and disappointed with their own figures. Exposure to model-laden ads may result in women eating more, especially (though strangely) if those women are already diet and food conscious.
Some studies even find an increase in eating-disorder symptoms after subjects just flipped through fashion ads.

Eating disorders are a grave problem. According to the National Institute of Mental Health, an estimated 0.5% to 3.7% of women will suffer from anorexia in their lifetime; 1.1% to 4.2% for bulimia and 2% to 5% for binge eating disorder. Anorexia exacts the highest death rate of any mental illness, a rate 12 times higher than deaths from all other causes for women age 15 to 24.

Seeing media images of thin women, however, is just one part of the eating disorder puzzle. According to the National Women’s Health Information Center, teenagers whose parents criticize their weight or diet and value thinness are more likely to become anorexic or bulimic. Stressful life events, from rape to simply starting a new job are implicated in the development of eating disorders. Personality differences also affect the likelihood of becoming anorexic, which may be linked straight back to brain chemistry, which may underpin anorexia’s close link with depression.

And of course, there are the genetics. In 2002, University of Pittsburgh psychiatrist Walter Kaye led a team of researchers who found the first genetic markers for anorexia among 37 families with multiple sufferers. In 2003, the same team found a strong genetic marker for bulimia. Today the same researchers have a $10 million NIH grant to explore the genetics and environmental cues that lead to anorexia. They are currently looking for more subjects to bring their study size up to 400 families.

Current opinion is that genetics predispose certain individuals to eating disorders, which may then be triggered by the environment. Environments like a thin-obsessed culture. It’s important to remember, says Kaye, that almost all Western women are exposed to the thinness ideal through images, but only a tiny fraction of them develop true eating disorders. “Less than half of one percent of all women develop anorexia nervosa, which indicates to us that societal pressure alone isn’t enough to cause someone to develop this disease,” said Kaye in a press release this January.

There is also no evidence that the ultra-skinny, size-zero models are responsible for undue harm. No studies have compared the effects on young women of viewing a size-zero model versus sizes two, four or six. It might not take a BMI as low as 18 to get the average American woman – who wears a size 14 or so – to start feeling ashamed about her body and strain her relationship with food. What’s more, there is little evidence to show that as models get skinnier – as the media report they have – eating disorders go up. Though eating disorders have clearly proliferated in the twentieth century, one 2006 study from Psychological Medicine actually found a drop in U.S. bulimia rates from 1982 to 2002. In a 2004 study published in the International Journal of Eating Disorders doctors at University Hospital in Zurich found that although rates of anorexia increased dramatically in the 1960s and 1970s, they have remained stable since then. Doctors at the Institute of Psychiatry in London found a similar stability in anorexia rates between 1988 and 2000, according to a study published in the British Journal of Psychiatry in 2005.

The only clear truth is that eating disorders like anorexia are complicated, poorly understood and dangerous. Blaming size-zero models (and the industry that loves them) is a simplistic view of these diseases. Sort of like how using BMI to protect those same women is glossing over the fact that the fashion industry seems incapable or unwilling to prevent women from dying in the name of beauty.