Body Mass Index Scales: Are They the Right Tool for Health?

Body mass index scales have been used for decades to assess health and weight status. However, a closer examination reveals that BMI may not be as reliable as once believed.

In this article, we delve into the historical context of BMI, uncover its limitations, discuss the influence of pharmaceutical companies, explore research findings challenging its validity, and shed light on the motivations behind its continued use. By doing so, we emphasize the importance of embracing a comprehensive and personalized approach to assessing health while combatting weight stigma.

The Origins of Body Mass Index

The origins of BMI can be traced back to the early 19th century when a Belgian mathematician named Lambert Adolphe Jacques Quetelet introduced the formula. The purpose of this formula was to provide a quick and simple way to measure the weight of the general population and to define the characteristics of a "normal man." Thus, the initial BMI formula was introduced.

Fast forward to the early 1900s in the United States, U.S. life insurance companies observed a higher rate of death for people (white, wealthy men) who were “overweight” using a ratio of weight and height that they developed into weight tables. However, subsequent research, encompassing larger and more diverse samples, revealed that individuals classified as "overweight" actually had lower mortality rates. Despite these new findings, insurance companies, driven by financial considerations, continued to emphasize weight as a determinant of premature death.

In 1972, researcher Ancel Keys, who disagreed with the insurance weight tables and aimed to find an alternative approach to evaluate body mass, suggested renaming the Quetelet Index as the Body Mass Index (BMI). Keys proposed using Body Mass Index scales to investigate and establish connections between health, disease, and "obesity."

In 1998, the National Institutes of Health (NIH) decided to reduce the threshold for the "overweight" BMI category to 25 for both males and females, which previously had been 28 for men and 27 for women. This decision was based on a 1996 report by the International Obesity Task Force (IOTF), which recommended lowering the BMI category of "overweight." Interestingly, the primary funders of the IOTF report were Hoffmann-La Roche and Abbott Laboratories, two pharmaceutical companies that produce weight-loss drugs. Moreover, many of the researchers and scientists who served on the WHO and NIH committees were being paid by various weight-loss drug companies. These companies had a vested interest in classifying more Americans as "overweight," thereby creating a much larger market for their weight-loss drugs. 

This brings us to the widely recognized and utilized measurement that persists today. Keeping this timeline of the BMI in mind, I want to take a deeper look at what this all means and all of the moving parts involved.

Flaws in the Body Mass Index Scale

To begin, let's delve into Quetelet's creation of the BMI formula. While Quetelet's intentions were well-meaning, his scientific methods had some questionable aspects. Firstly, his data was solely derived from a specific European white male population, which represents only 30% of the current US population. This means that the formula fails to account for the other 70% of the population, encompassing diverse races, ethnicities, and body sizes. Second, Quetelet outlined that the BMI formula is not intended to measure an individual's health status; rather, the formula was only intended to be used for measuring a population's health status. Finally, while the concept of "the average man” could be a useful concept for understanding general trends, averages often don't hold true when applied to any specific individual. For example, a family may have an average of 2.4 children, but obviously, no one has .4 of a child. 

During the creation of the BMI formula, Quetelet had to alter the formula to fit his data, a practice that goes against proper statistical methodology and is considered flawed science. Moreover, the formula fails to consider crucial factors such as age, sex, body frame, body composition, and the natural changes in body mass that occur with age. It also makes no differentiation for the relative proportions of bone, muscle, fat, and fluid in the body, which varies from person to person naturally.

Now let’s unpack what occurred through the 1900s. The cutoff points for BMI categories, such as "normal" versus "overweight," were not based on scientific data, but instead, they were arbitrarily established in response to a report financed by pharmaceutical companies that produce weight loss drugs. As a result, millions of people were suddenly categorized as "overweight" overnight.

What Are Body Mass Index Scales Really Measuring?

Now, let's explore some compelling research that challenges the underlying logic of BMI measurement.

A notable large-scale study conducted in 2013 involving 40,000 participants revealed fascinating findings. It showed that individuals falling within the "obese" BMI range had the same risk of death as those with "normal" BMIs, while those classified as "overweight" actually had a lower risk of death compared to all other BMI categories. Surprisingly, the highest risk of death was observed among individuals categorized as "underweight."

Findings also showed that individuals with "obese" BMIs living with type 2 diabetes, high blood pressure, cardiovascular disease, or chronic kidney disease had longer life expectancies than their thinner counterparts with the same conditions. Additionally, when examining individuals over the age of 55, those with BMIs in the "overweight" and "obese" categories exhibited a decreased risk of death compared to individuals with "normal" and "underweight" BMIs.

Another compelling study discovered that nearly half of those classified as "overweight" and one-third classified as "obese" were metabolically healthy. This means that despite their higher BMI, these individuals demonstrated normal readings in key health indicators such as blood pressure, cholesterol, and blood sugar levels, indicating good overall health. Conversely, almost one-third of those in the "normal" weight BMI category were found to be metabolically unhealthy.

These findings challenge the traditional assumptions and interpretations associated with Body Mass Index scales, highlighting the complexity of body weight and its correlation with health outcomes.

Why Does the Medical Community Still Use Body Mass Index?

If we know all of these points, why does the medical community use BMI?  

Despite the limitations and flaws of BMI, the medical community continues to utilize it for several reasons. One primary factor is the simplicity and cost-effectiveness of calculating BMI. It involves a straightforward calculation based on height and weight, making it a quick and convenient tool for assessing weight. This ease of calculation allows for widespread use and application in various healthcare settings.

Another significant influence is the lobbying efforts of the medical insurance industry. Insurance companies have a vested interest in maintaining the use of BMI, as it can be a determinant of insurance premiums. In some cases, individuals with higher BMI may face higher insurance premiums, irrespective of their actual health status. This approach is problematic because it fails to account for the variations in body composition, where fit individuals with good bone and muscle mass but relatively higher weight due to less fat are unfairly penalized. Consequently, insurance companies benefit financially by charging higher premiums based on BMI, thus keeping their profits high.

This reliance on BMI as a proxy for health and charging higher premiums for individuals with higher BMI disregards the nuances of individual health. It fails to account for other crucial factors that contribute to overall well-being. It underscores the importance of advocating for a more comprehensive and personalized approach to assessing health that considers not only weight but also other relevant indicators such as body composition, metabolic health markers, and overall lifestyle factors. By shifting the focus towards a more holistic understanding of health, we can better serve individuals by providing fairer and more accurate assessments while challenging the profit-driven motivations that perpetuate the use of BMI as a simplistic and flawed measure.

Navigating Health Beyond Body Mass Index Scales

The Body Mass Index (BMI) has proven to be a flawed and problematic measurement when it comes to assessing an individual's health and weight status. Its shortcomings, including its inability to account for variations in body composition, its reliance on arbitrary cutoff points, and its failure to consider factors such as age, sex, and muscle mass, have been widely acknowledged. Moreover, the history and influences behind the development and perpetuation of BMI reveal the role of profit-driven interests and weight stigma in shaping its continued use. It is crucial to recognize the limitations of BMI and advocate for a more comprehensive and personalized approach to assessing health that considers a range of factors beyond weight alone. By embracing the Health at Every Size® approach and promoting equity for all bodies, we can foster a more inclusive perspective that prioritizes well-being.

Ready to explore a more personalized approach to your nutrition and health? Contact our expert dietitians at CV Wellbeing for a consultation that focuses on your unique health needs. Discover more about our services here.

Written by Alison Swiggard, MS, RDN, LD, Dietitian at CV Wellbeing

Why do we use quotation marks around the words "obese" and "overweight"?

These terms have been coined by the medical community to pathologize and label individuals based on their body size. By using quotation marks around "overweight," we acknowledge that it implies an arbitrary notion of a "correct" weight that everyone should adhere to, as dictated by flawed and problematic BMI charts. Similarly, the term "obese" is enclosed in quotation marks because it assigns illness solely based on size, inaccurately assuming that weight is the sole determinant of one's health and wrongly placing blame on the individual. By using quotation marks, we bring attention to the underlying biases and harmful implications associated with these terms, fostering a critical examination of the way we perceive and discuss body weight and its impact on health.