Traditional Vs Biological BMI: Researchers Build A More Comprehensive Measure Of Metabolic Health

The traditional measurement of body mass index (BMI) is considered to be quite limited. A team of researchers has now constructed what could be a more comprehensive BMI measure of metabolic health.

BMI has been used generally as a measure of body fatness using height and weight to identify people as underweight, normal, overweight or obese. Studies have shown a correlation between BMI, body fat and future health risks, noted the U.S. Centers for Disease Control and Prevention (CDC).

BMI has been helpful in various ways. However, there have also been concerns about this means of measuring health. It measures excess weight rather than the body fat itself, and it doesn't take into account other factors such as age, ethnicity, sex and muscle mass. Some 30% of people end up being misclassified under the traditional BMI, according to the Institute for Systems Biology (ISB).

An athlete with a high muscle-to-fat ratio, for instance, may be classified as someone with obesity.

For their new study, which was published Monday in the journal Nature Medicine, a team of researchers built a "biological" BMI measure that may just be more comprehensive than the traditional one. They studied 1,000 people who were enrolled in a wellness program and performed "multi-omic profiling."

"Omics studies have demonstrated how blood omic profiles contain information relevant to a wide range of human health conditions; for example, blood proteomics captured 11 health indicators, such as the liver fat measured by ultrasound and the body composition," the authors wrote.

They then used a machine learning model to predict biological BMI.

The researchers found quite a few interesting and important results – people with normal traditional BMI but high biological BMI are "less healthy" but can lose weight more easily with intervention. On the other hand, those considered obese under the traditional BMI but had normal biological BMI were actually more biologically healthy. They, however, found it harder to lose weight.

Another, perhaps hopeful, finding was that biological BMI was actually more responsive than traditional BMI, dropping earlier when people made lifestyle changes. This may be uplifting for those who have been trying to make a positive lifestyle change but are discouraged due to a lack of visual results.

The results show the value of blood multiomic for predictive and preventive medicine. It also shows the complexity of the relationship between obesity, chronic disease and metabolic health and the importance of looking at factors "beyond traditional measures," said corresponding author Noa Rappaport.

"For years, BMI has been the go-to measure for doctors to classify individuals based on their height and weight in comparison to an average person. However, this average person doesn't truly exist," Rappaport said. "We now have the capability to use advanced molecular measurements as a more comprehensive representation of a person's metabolic health, which can be used to make more accurate clinical recommendations for individuals."

As for keeping oneself healthy, the CDC recommends a combination of measures, including healthy eating, optimal sleep, reduced stress and physical activity. Keeping a healthy weight isn't about a specific diet or program, but of a lifestyle change in one's habits, the agency noted.