Body mass index, or BMI, is often promoted as a key measure of health, but clinicians are increasingly understanding its flaws and moving toward more comprehensive markers.
In 2023, research in the American Medical Association’s Journal of Ethics found “standard weight” metrics and “fear of fatness” were developed under the eugenics movements of the 19th and 20th centuries in correlation with fear of women of color. A major weakness of the measure is that it is based upon primarily non-Hispanic white and male models, making it less effective for people of color and women.
The association labeled BMI as an “imperfect way to measure body fat in multiple groups given that it does not account for differences across race/ethnic groups, sexes, genders and age-span.” It recommended BMI only be used in conjunction with other “valid measures of risk,” such as metabolic factors, and that physicians recognize relative body shape and composition differ across different communities.
Siddhartha Angadi, an associate professor of exercise physiology at the University of Virginia, says there are far more useful ways to measure physical fitness than BMI. (Photo by Matt Riley, University Communications)
Siddhartha Angadi, an associate professor of exercise physiology at the University of Virginia School of Education and Human Development, said he uses exercise as a model to understand cardiovascular disease.
“The reason why we use exercise is because one of the first symptoms you know that a patient with a cardiovascular problem will present with is what we call activity intolerance,” he said. “A patient with heart failure will come in and say, ‘I used to be able to walk half a mile before getting out of breath and now I get out of breath walking like 100 feet.’”
Angadi uses VO2 max, or maximal oxygen consumption – the highest level of oxygen a person can use during intense exercise – to measure cardiorespiratory fitness. The metric, which is determined by the health of the heart, lung and muscles, he said, is important because it reflects the most common cause of death in the United States, cardiovascular disease.
“Exercise is a useful model for understanding a lot of conditions, whether they’re cardiac, pulmonary or metabolic,” he said. “It does a pretty good job at integrating multiple organ systems compared to BMI.”
Physical activity is one of the true miracle pills that we have.
Many people believe as BMI goes up, risk for disease and mortality automatically goes up, but Angadi said the reality is more nuanced. “Large meta-analyses have shown that really, it’s a U-shaped curve with most of the risk concentrated at BMIs above 35 and BMIs below 18.5,” he said.
In 2024, Angadi and colleagues published a study that found optimal health outcomes should be assessed based on a fitness-based approach, rather than a weight-loss approach, when working with obese patients. Analyzing more than 20 studies with a sample size of 398,716 adults from multiple countries, the researchers found individuals who were more fit or active had a lower risk of death and cardiovascular disease over time, no matter their weight.
Participants were considered fit if their VO2 max result placed them in the 80th percentile within their age group in most studies.
“People should worry more about their fitness status than their weight,” Angadi said. “Physical activity is one of the true miracle pills that we have.”
He recommends people try to meet the physical activity guidelines of 150 minutes of moderate-intensity activity a week or 75 minutes of vigorous activity as recommended by the American College of Sports Medicine and the CDC. “This can look like 30 minutes of moderate activity a day, five days a week,” he said.
Researchers at the lab of Family Medicine chair Dr. Li Li have also found obesity is not necessarily the best measure for determining cancer risk. The researchers are working on a paper that uses metabolic obesity as a factor to determine the risk of developing colorectal cancer.
For this, they are using the Homeostatic Model Assessment for Insulin Resistance, which measures insulin resistance. Insulin resistance, she notes, is what is understood to lead to diabetes.
