New Research Questions Reliance on BMI for Assessing Healthy Weight

Many clinicians’ traditional method for gauging healthy weight may not be as reliable as once thought, new research suggests.

A study conducted by the University of Florida (UF) reveals that the body mass index (BMI) might not be the best choice for predicting health risks tied to weight—far from it, actually.

Instead, there’s a method that’s been around for a while and measures body fat directly—it’s known as bioelectrical impedance analysis (BIA). This method has shown to outperform BMI notably.

In a nationwide assessment, individuals with elevated body fat—determined by BIA—had a staggering 262 percent higher risk of dying from heart disease compared to those with lower body fat levels.

The conventional BMI, which merely compares weight and height, didn’t show any significant links to mortality.

“Really, the risk this study presents is significant,” cardiologist Andrew Freeman, who wasn’t part of the research, shared in an interview. “It’s concerning that we’ve relied on a surrogate like BMI, which may have lacked accuracy over the years.”

BMI has traditionally been viewed as a primary obesity measure, supported by major health organizations like the CDC, NIH, and WHO.

However, in recent times, experts globally have started to re-evaluate BMI, noting that it doesn’t take into account variations in body composition, age, gender, or ethnicity. Some health authorities have even urged a shift away from relying solely on BMI.

Arch Mainous, a health services researcher at UF, and his team have introduced a timely alternative that can be executed in under a minute. BIA directly assesses body fat using an affordable and portable device.

This device functions by sending a weak electric current through body tissues to assess muscle and fat proportions. Although this technology has been around since the 1980s, modern fitness trackers and smartwatches have recently started integrating BIA sensors.

While not without imperfections, the findings from UF point to BIA as a more accurate health indicator than BMI.

They discovered that adults with high body fat levels, indicated by BIA, had a 78 percent heightened risk of dying from any cause over 15 years, while higher BMI scores did not correlate with all-cause mortality.

“This research changes the game,” said lead author Mainous. “You can think of it as the ultimate Coke versus Pepsi debate, and BMI simply didn’t succeed.”

Though BMI is straightforward and easy to calculate, it has notable drawbacks. For instance, muscular individuals might be incorrectly categorized as overweight or obese. Conversely, those with a normal BMI but high body fat might be oblivious to potential health risks like metabolic syndrome or type 2 diabetes.

Mainous and his colleagues assert that BIA provides a more precise alternative, and the small, cost-effective devices used for measurement could be implemented regularly in medical settings.

The team at UF anticipates that, if validated in broader and more varied populations, measuring body fat percentage through BIA may become standard practice in healthcare.

“These insights could enhance discussions in medical offices and inform public health strategies aimed at improving overall health,” the research team concluded.

This study appeared in the Annals of Family Medicine.