What Is Metabolome? Health Check Method Better Than BMI Developed by Scientists

The Body Mass Index (BMI), traditionally used by doctors to estimate if a person's weight is unsafe, is not the best measure of health. That's according to scientists who have proposed a more accurate method.

Instead, researchers believe a person's metabolome is a more precise measure of how weight corresponds to a person's health. The metabolome is a product of how a living thing's genome interacts with its environment. It is made up of a number of small molecules known as metabolites—like glucose—which, according to Advances in Genetics, are produced by a biological entity as small as a cell to a human. Metabolites are a particularly useful measure of the internal goings-on of an organism because they stay the same, unlike proteins or genes. For instance, glucose in a human is much the same as in a sea anemone, notes the educational platform Future Learn.

The authors of the study, published in the journal Cell Metabolism, believe the measure could help tackle the obesity epidemic. As many as 2.8 million people die worldwide every year due to conditions caused by being overweight or obese, the World Health Organization states. Worryingly, the U.S. was the most obese nation in the world in 2017, according to the Organization for Economic Cooperation and Development, with a 38.2 percent obesity rate in the total population.

Related: Why being skinny-fat could be just as dangerous as being obese

The BMI score (calculated by dividing a person's weight in kilograms by the square of their height in meters) is widely used to total up a person's body fat. The higher the score, the higher the likelihood a person will have a high level of body fat, said the Centers for Disease Control.

While it is a useful tool, it does not measure excess body fat or distribution, or take into account variables such as age, sex, ethnicity and muscle mass that can shape a person's health in important ways.

The clunkiness of BMI testing was laid bare when the researchers found people with identical BMIs had different scores for health such as insulin resistance, and body fat percentage.

The team collected information including BMI, and the results of whole body scans and genome sequencing on 2,393 participants. Over 1,000 metabolites were also studied to uncover each participant's metabolic signature.

Calculating the metabolome was found to accurately predict whether a person was obese with between 80 to 90 percent accuracy, according to the study authors.

At the same time, a person's genes appeared not play a huge part in whether they were obese, with the exception of genes linked with extreme obesity such as the MC4R mutation.

Moving forward, the researchers believe the technique could be used to identify subgroups of people who are at greater risk of certain health problems than the average person, first author Liz Cirulli, a research scientist at the firm Human Longevity Inc., told Newsweek.

"They can be followed up according to their personal risk as opposed to just according to their BMI," she said.

The study didn't uncover the causes of different metabolic signatures, continued Cirulli, but it seems likely that differences between people in their metabolic signatures can be attributed to differences in their lifestyle: how they eat, how they exercise and more.

"The take-home message is probably that in order to stay healthy, you should be focused on your habits and not on your weight. You can be obese and have a healthy metabolic signature, and you can be skinny and have an unhealthy metabolic signature."

Senior author of the study Amalio Telenti, a professor of genomics at Scripps Research, told Newsweek: "Three observations [from the study] were surprising. First, that there is a very profound metabolic alteration associated with obesity—and there was no threshold: Every additional kilogram or pound counts.

"Second, and a glimpse of optimism: The metabolic abnormalities can reverse rapidly upon weight loss. Third, the concept that some people do better than others despite being overweight or obese is true—the healthy—healthier—obese exists. However, there are people that despite having normal weight, have the metabolic status of the obese and the corresponding health consequences."

Yet, however useful these measures appear to be, genome sequencing and metabolic profiling are far from being widely available, said Telenti. "However, these are new tools that will make their way into the field of predictive medicine."

The study contributes to an ongoing debate on the usefulness of the BMI score. In 2016, a study published by researchers at the University of California in the International Journal of Obesity posed a similar question.

The team found BMI was not an accurate measure of an individual's cardiovascular health. Half of the participants categorized as overweight according to their BMI had a healthy cardiometabolic profile, measured according to their blood pressure and sugar levels and their cholesterol, while a third who scored as normal had unhealthy cardiometabolic profiles.