The risks of relying on BMI

Holly Russell M.D.’s suite at Highland Family Medicine does not routinely weigh each patient when they arrive for a follow-up visit. In her practice, she goes beyond the traditional body mass index, considering behavioral aspects. 

The link between weight and health is complicated, she believes.

Weight bias and a focus on weight in health care produce known harms, she writes in a commentary titled “Is it time to say goodbye to BMI?” In the recently published article in Family and Community Health, Russell argues that a discussion on weight requires an understanding of the bigger picture.

For more than a century, medical professionals have relied on the body mass index as a predictor of health risks, and also to shape health policy. Introduced in the early 19th century by mathematician and astronomer Lambert Adolphe Jacques Quetelet, the formula offered a way to measure the obesity of a population. 

The CDC 2022 Adult Obesity Prevalence Maps for each state also uses BMI, showing the proportion of adults with a body mass index equal to or greater than 30 based on self-reported weight and height. According to that data, New York’s obesity prevalence is 30.1.

Then, there’s the weight-loss industry, which also uses the statistic quite successfully. A July 2023 Market Research.biz report estimated that the size of the global weight loss market was $260.7 billion in 2022 and it is projected to cross the $500 billion mark by 2032.

Over the years, some experts have argued that BMI is an unreliable tool. A person with muscle and minimal fat, for example, can share the same BMI as a person with much less muscle. Body fat tends to vary among people and can be misleading, they say.

Russell warns of the risks in using the index.

“There is a clear risk–many studies have shown that patients routinely delay and avoid health care due to fears about being lectured that they need to lose weight,” she says. “There is also a lot of research showing that people with higher BMI numbers are routinely denied health care and experience explicit weight bias in health care settings.

“The idea that there is a universally applicable ideal weight,” she adds, “is as valid as the idea that there is an ideal height or hair color.”

Russell also brings attention to a misconception that the index is tested and valid in all populations. History shows, however, that “it was developed almost exclusively from data from white, European men and has been shown not to be valid for other groups.”

In her commentary she notes that clinicians often recommend losing weight without a nuanced discussion of the evidence showing that most people are unlikely to be successful with sustained weight loss.

Patients would be better served, Russell believes, with a focus on healthy behaviors with much stronger evidence for health and well-being.

The Rochester Beacon posed a few questions to Russell to get a better understanding of her views. Her answers follow.

ROCHESTER BEACON: What prompted you to write a commentary on BMI? 

HOLLY RUSSELL: I have really changed my thinking about approaches to weight and health over the last 7-8 years. I originally started off with a focus on weight loss and obesity management but always felt like something wasn’t quite right about that approach. I was invited to a talk given by the Adolescent Medicine department about disordered eating and the overlap with obesity management and something clicked for me that focusing on weight was really missing the mark. I started reading and understanding more about the history of the BMI and especially the influence of systemic racism on the way we prioritize thinness in our society. I started to share this information with colleagues and was asked to give a Grand Rounds presentation about the topic. I received a lot of positive feedback from that presentation and it made me realize there were others who might be interested and could benefit from learning more about the history and lack of evidence for BMI.  

ROCHESTER BEACON: What are some of the biggest misconceptions about BMI? 

RUSSELL: I think the biggest misconception is that there is a clear and precise link between levels of BMI and worsening health and that outcomes suddenly change when you cross over a line to a different category. The second-biggest misconception is that the BMI is tested and valid in all populations rather than the true history which is it was developed almost exclusively from data from white, European men and has been shown not to be valid for other groups. The third-biggest misconception is that BMI was originally developed to evaluate an individual’s health rather than the truth that it was developed more as a population measure and was never intended to be a diagnostic tool.

ROCHESTER BEACON: For years patients, medical experts and weight-loss programs have relied on this number to gauge obesity. What would you say to them about your views on the issue? What is “ideal weight”? 

RUSSELL: I would say that we need to think critically about the benefits and risks of anything we do in medicine and that we have an ethical obligation to “do no harm.” There is no clear evidence that routinely weighing patients and calculating BMIs improves patients’ health. Most clinicians believe there is evidence for screening for weight; however, when the guidelines were written they specifically stated there were no trials comparing screening for weight versus not screening, and the most recent guidelines said that screening for obesity was a routine part of clinical practice and therefore not a focus of the review. So, we just keep doing it because it’s something we have always done without understanding the risks or benefits.

There is a clear risk–many studies have shown that patients routinely delay and avoid health care due to fears about being lectured that they need to lose weight. There is also a lot of research showing that people with higher BMI numbers are routinely denied health care and experience explicit weight bias in health care settings. The idea that there is a universally applicable ideal weight is as valid as the idea that there is an ideal height or hair color. 

ROCHESTER BEACON: Should we be looking beyond BMI? If so, what factors should we pay close attention to, and do you think change is possible? 

RUSSELL: Absolutely we should look further than BMI. On my suite at Highland Family Medicine, we have actually stopped routinely weighing every patient when they come in for a follow-up visit. My personal practice is to focus on behavioral aspects that have much stronger evidence for health and well-being than weight loss. We know that people with strong social connections live longer and healthier lives and so we can encourage our patients to spend time forming meaningful relationships. We know that the more you move, the longer you live, and so we can think about how to move our bodies in ways that are therapeutic and don’t have to look like traditional exercise. And, most importantly, for people who smoke we can spend time counseling and linking them to medications that can help with quitting or cutting down–this can add a decade onto people’s lives!

Smriti Jacob is Rochester Beacon managing editor. The Beacon welcomes comments and letters from readers who adhere to our comment policy including use of their full, real name. Submissions to the Letters page should be sent to [email protected].