Rhea Harsoor
Term: Body Mass Index
Background and Introduction
Body mass index (BMI) is a measurement commonly used to estimate total body fat. BMI can be calculated by dividing weight (kg) by the square of one’s height (meters). The resulting BMI score allows for categorization into four categories: underweight, healthy, overweight, and obese. A BMI below 18.5 is considered underweight, between 18.5 and 24.9 is considered healthy, between 25 and 29.9 is overweight, and above 30 is obese[ii]. In modern practice, BMI is typically used by government agencies, healthcare practitioners, and the health conscious in order to measure obesity[iii]. BMI is considered an indicator of body fat due to the correlational relationship between BMI and body fat percentage. However, muscle, bone, body fluids and organs that contribute to body mass are also measured in BMI. Thus, BMI can provide inaccurate measures of body fat.
In comparison to other popular measurements of body fat, BMI is considered less sensitive than underwater weighing, bioelectrical impedance, waist circumference measurement, and skinfold thickness. Additionally, while the skinfold thickness caliper and measuring waist circumference are both relatively cheaper options, the skinfold thickness caliper is often used incorrectly, and people often struggle to accurately measure the circumference of the waist/hip[vi].
Historical/Topical Context
In 1832, a Belgian mathematician named Adolphe Quetelet devised the Quetelet Index. This index was based on the notion of ‘l’homme moyen’, which translates to the average man. By conceptualizing “the average man”, he inspired the social construct of normalcy “with [this] bourgeois hegemony comes scientific justification for moderation and middle-class ideology”[vii]. When devising this measurement tool, Quetlet explicitly stated “that it could not and should not be used to indicate the level of fatness in an individual”[viii]. Moreover, his intent for the BMI formula was to provide the government with a mechanism by which they could measure the degree of obesity in order to allocate resources.
The World Health Organization (WHO) has attempted to sub-divide the four major categories (Underweight, Normal, Overweight, Obese) to create a standard international of BMI ranges (WHO, 2017). However, different countries still maintain different BMI ranges, adding difficulty to interpreting international BMI statistics. Japan, for example, classifies overweight BMI scores as 23.0 – 24.9, and obese as 25.0 and upward (Shiwaku et al. 2003).
Source: World Health Organization
Controversy/Perspectives
There is widespread controversy regarding the usage of BMI as a standard of health. It’s founder, Quetelet, acknowledged that it should not be used as a measure of “fatness”, but more as a measure of normalcy. There is evidence that “healthy” BMI relates to longevity, as pointed out by a 2003 study. Over 700,000 deaths were measured in relationship to the BMI of the deceased individual, and the researchers found that the “Optimal BMI [in relationship to lowest mortality] increased with age from 21.6 (at age 20-29) to 24.0 (at age 70-74). In women, the optimal BMI was higher than for men at all ages and increased from 22.2 (at age 20-29) to 25.7 (at age 70-74)” (Engeland et al. 2003, 296). The ideal BMI for older women was slightly outside the defined Healthy range of BMI, the BMI scores with the lowest mortality were found to be in the WHO defined “healthy” range of 18.5-24.9. Though imperfect, BMI does provide a quick, costless measure for which very basic health assessments may be made based on correlational trends. It functions well as a single piece of information that can be used in a larger composite evaluation of one’s health.
Despite its potential scientific benefit, BMI has profound social implications, as well as medical shortcomings. Because BMI only takes into account height and weight, it inherently fails to account for differences in gender, age, muscle mass, and ethnicity. As a result, those who lie outside what is considered “normal,” are often categorized into weight groups that are not indicative of their health status. As highlighted by the aforementioned study, ideal BMI (in terms of mortality rates) changes with age, something that is not often emphasized. Besides the muscular who are wrongly categorized as overweight, BMI also miscategorizes those carrying extra weight in dangerous areas. As a result, those relying solely on BMI as a screening tool are at risk for missing signs of heart disease and diabetes[xii]. To identify the number of people misclassified, the International Journal of Obesity recently determined that, if used alone, BMI “would misclassify almost 75 million adults in the U.S”[xiii]. To avoid this issue of missing those with hidden excess fat, it is recommended that waist circumference also be measured in addition to BMI when assessing body fat[xiv]. The relative pervasiveness of BMI in our society inflates its perceived value, and makes it appear to be a deciding factor of healthiness, an overvaluation that leads to misdiagnosis.
How it Relates to Politics of Health
This term is related to the politics of health because of its underlying themes of normalcy. Just as the cultural phenomenon that is middle class ideology led to normalcy of everyday values, BMI as a measure of the average man’s health status quickly became popular. As Davis wrote in Enforcing Normalcy, “Statements of this kind saw the bourgeoisie as rationally placed in the mean position in the great order of things. This ideology can be seen as developing the kind of science that would then justify the notion of a norm”[xv]. However, the issue with linking norms with ideals is that it, as Davis writes, “implies that the majority of the population must or should somehow be part of the norm”[xvi]. The norm, however, varies. As previously mentioned, countries like Japan classify BMI based on different ranges. This cultural differences reinforces the idea that the ideals of normalcy that BMI was founded on in 1832 are heavily subjective. BMI normalcy becomes dangerous when we forget that it is subjective and pursue what we believe to be a guaranteed measure of improved health.
Additionally, this is also related to the concept of rethinking health and bodies. Just as the way in which we define health affects the way in which we approach health related concepts, the way in which we define measurements of “good health” affects the way in which we practice medicine. When we define health by BMI we are explicitly making a decision about what consists of good health, and therefore what consists of bad health. Categorizing individuals based on their BMI allows for generalizations to be made regarding the health status of a larger group of people than just those who are considered average. Since these scores are continuous numbers, categorizing based on arbitrary benchmarks may cause one to assume that the differences between categories are larger than those within categories[x]. Moreover, these benchmarks can often seem arbitrary because a 0.1 difference in BMI between two individuals and can lead them to be considered at risk for a variety of diseases. We must consider the impact of this definition, if only height and weight are prioritized as measures of health, we are encouraging a standard of health that does not necessarily prioritize the reduction of disease and the increase in lifespan but rather the optimization of one’s height, in relation to one’s weight.
Works Cited
“BMI (Body Mass Index): What Is BMI?” Medical News Today. Accessed March 13, 2017. http://www.medicalnewstoday.com/info/obesity/what-is-bmi.php.
Britannica Academic, s.v. “Body mass index (BMI),” accessed March 13, 2017, http://academic.eb.com.proxy.library.vanderbilt.edu/levels/collegiate/article/body-mass-index/471446.
Davis, Lennard. Constructing Normalcy. Enforcing Normalcy. Pages 123 – 149.
Devlin, Keith. “Top 10 Reasons Why The BMI Is Bogus.” NPR. July 04, 2009. Accessed March 13, 2017. http://www.npr.org/templates/story/story.php?storyId=106268439.
Hobson, Katherine. “BMI Is A Terrible Measure Of Health.” FiveThirtyEight. February 25, 2016. Accessed March 13, 2017. https://fivethirtyeight.com/features/bmi-is-a-terrible-measure-of-health/.
Pope, Jamie. Nutrition for a Changing World. WH Freeman, 2015.
[i] Britannica Academic, s.v. “Body mass index (BMI),” accessed March 13, 2017, http://academic.eb.com.proxy.library.vanderbilt.edu/levels/collegiate/article/body-mass-index/471446.
[ii] Jamie Pope, Nutrition for a Changing World (WH Freeman, 2015).
[iii] Katherine Hobson, “BMI Is a Terrible Measure Of Health,” FiveThirtyEight, February 25, 2016, accessed March 13, 2017, https://fivethirtyeight.com/features/bmi-is-a-terrible-measure-of-health/.
[iv] “BMI (Body Mass Index): What Is BMI?” Medical News Today, accessed March 13, 2017, http://www.medicalnewstoday.com/info/obesity/what-is-bmi.php.
[v] Ibid.
[vi] Pope, Nutrition for a Changing World.
[vii] Lennard J. Davis, Enforcing Normalcy (Verso, 2016).
[viii] Keith Devlin, “Top 10 Reasons Why The BMI Is Bogus,” NPR, July 04, 2009, accessed March 13, 2017, http://www.npr.org/templates/story/story.php?storyId=106268439.
[ix] Ibid.
[x] Ibid.
[xi] “BMI (Body Mass Index): What Is BMI?”
[xii] Hobson, “BMI Is a Terrible Measure Of Health.
[xiii] Ibid.
[xiv] Ibid.
[xv] Davis, Enforcing Normalcy.
[xvi] Ibid.
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Added sources upon revision
1 “WHO :: Global Database On Body Mass Index”. Apps.who.int. N.p., 2017. Web. 2 Apr. 2017.
2) Shiwaku, K et al. “Overweight Japanese With Body Mass Indexes Of 23.0–24.9 Have Higher Risks For Obesity-Associated Disorders: A Comparison Of Japanese And Mongolians”. International Journal of Obesity (2003): n. pag. Web. 2 Apr. 2017.
3) Engeland, Anders, Tone Bjørge, Randie Marie Selmer, and Aage Tverdal. “Height and Body Mass Index in Relation to Total Mortality.” Epidemiology 14, no. 3 (May 2003): 295-96. Accessed April 2, 2017. JSTOR.
4) “WHO :: Global Database on Body Mass Index.” WHO :: Global Database on Body Mass Index. Accessed April 02, 2017. http://apps.who.int/bmi/index.jsp?introPage=intro_3.html.
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