When Do We Stop Using BMI to Diagnose Obesity?
September 13, 2022
Sylvia Gonsahn-Bollie, MD
"BMI is trash. Full stop." This controversial tweet received 26,500 likes and almost 3000 retweets. The 400 comments from medical and nonhealthcare personnel ranged from agreeable to contrary to offensive.
Regardless of your opinion on BMI (body mass index), this conversation highlighted that the medical community needs to discuss the limitations of BMI and decide its future.
As a Black woman who is an obesity expert living with the impact of obesity in my own life, I know the emotion that a BMI conversation can evoke. Before emotions hijack the conversation, let's discuss BMI's past, present, and future.
BMI: From Observational Measurement to Clinical Use
Imagine walking into your favorite clothing store where an eager clerk greets you with a shirt to try on. The fit is off, but the clerk insists that the shirt must fit because everyone who's your height should be able to wear it. This scenario seems ridiculous. But this is how we've come to use the BMI. Instead of thinking that people of the same height may be the same size, we declare that they must be the same size.
The idea behind the BMI was conceived in 1832 by Belgian anthropologist and mathematician Adolphe Quetelet, but he didn't intend for it to be a health measure. Instead, it was simply an observation of how people's weight changed in proportion to height over their lifetime.
Fast-forward to the 20th century when insurance companies began using weight as an indicator of health status. Weights were recorded in a "Life Table." Individual health status was determined on the basis of arbitrary cut-offs for weight on the Life Tables. Furthermore, White men set the "normal" weight standards because they were the primary insurance holders.
In 1972, Dr Ancel Keys , a physician and leading expert in body composition at the time, cried foul on this practice and sought to standardize the use of weight as a health indicator. Dr Keys used Quetelet's calculation and termed it the Body Mass Index, or BMI.
By 1985, the US National Institutes of Health and the World Health Organization adopted the BMI. By the 21st century, BMI had become widely used in clinical settings. For example, the Centers for Medicare & Medicaid Services adopted BMI as a quality-of-care measure, placing even more pressure on clinicians to use BMI as a health screening tool.
BMI as a Tool to Diagnose Obesity
We can't discuss BMI without discussing the disease of obesity . BMI is the most widely used tool to diagnose obesity. In the United States, one third of Americans meet the criteria for obesity. Another one third are at risk for obesity.
Compared with BMI's relatively quick acceptance into clinical practice, however, obesity was only recently recognized as a disease.
Historically, obesity has been viewed as a lifestyle choice, fueled by misinformation and multiple forms of bias. The historical bias associated with BMI and discrimination has led some public health officials and scholars to dismiss the use of BMI or fail to recognize obesity as disease .
This is a dangerous conclusion because it comes to the detriment of the very people disproportionately impacted by obesity-related health disparities.
Furthermore, weight bias continues to prevent people living with obesity from receiving insurance coverage for life-enhancing obesity medications and interventions.
Is It Time to Phase Out BMI?
The BMI is intertwined with many forms of bias: age, gender, racial, ethnic, and even weight. Therefore, it is time to phase out BMI. However, phasing out BMI is complex and will take time, given that:
Obesity is still a relatively "young" disease. 2023 marks the 10th anniversary of obesity’s recognition as a disease by the American Medical Association. Currently, BMI is the most widely used tool to diagnose obesity. Tools such as waist circumference, body composition, and metabolic health assessment will need to replace the BMI. Shifting from BMI emphasizes that obesity is more than a number on the scale. Obesity, as defined by the Obesity Medicine Association , is indeed a " chronic, relapsing, multi-factorial, neurobehavioral disease, wherein an increase in body fat promotes adipose tissue dysfunction and abnormal fat mass physical forces, resulting in adverse metabolic, biomechanical, and psychosocial health consequences."
Much of our health research is tied to BMI. There have been some shifts in looking at non-weight-related health indicators. However, we need more robust studies evaluating other health indicators beyond weight and BMI. The availability of this data will help eliminate the need for BMI and promote individualized health assessment.
Current treatment guidelines for obesity medications are based on BMI. (Note: Medications to treat obesity are called "anti-obesity" medications or AOMs. However, given the stigma associated with obesity, I prefer not to use the term "anti-obesity.") Presently this interferes with long-term obesity treatment. Once BMI is "normal," many patients lose insurance coverage for their obesity medication, despite needing long-term metabolic support to overcome the compensatory mechanism of weight regain. Obesity is a chronic disease that exists independent of weight status. Therefore, using non-BMI measures will help ensure appropriate lifetime support for obesity.
The preceding are barriers, not impossibilities. In the interim, if BMI is still used in any capacity, the BMI reference chart should be an adjusted BMI chart based on age , race, ethnicity, biological sex, and obesity-related conditions. Furthermore, BMI isn't the sole determining factor of health status.
Instead, an "abnormal" BMI should initiate conversation and further testing, if needed, to determine an individual's health. For example, compare two people of the same height with different BMIs and lifestyles. Current studies support that a person flagged as having a high adjusted BMI but practicing a healthy lifestyle and having no metabolic diseases is less at risk than a person with a "normal" BMI but high waist circumference and an unhealthy lifestyle.
Regardless of your personal feelings, the facts are clear. Technology empowers us with better tools than BMI to determine health status. Therefore, it's not a matter of if we will stop using BMI but when.
Sylvia Gonsahn-Bollie, MD, DipABOM, is an integrative obesity specialist who specializes in individualized solutions for emotional and biological overeating. Connect with her at www.embraceyouweightloss.com or on Instagram @embraceyoumd. Her bestselling book, Embrace You: Your Guide to Transforming Weight Loss Misconceptions Into Lifelong Wellness, is Healthline.com's Best Overall Weight Loss Book 2022 and one of Livestrong.com's picks for the 8 Best Weight-Loss Books to Read in 2022.