A “normal” body mass index does not always mean low risk for metabolic disease, according to a new study that proposes an alternative way to estimate risk using blood-based metabolic signals.
Researchers at the University of Gothenburg analyzed data from 1,408 people and found that participants with a higher-than-expected “metabolic BMI” had a two to five times higher risk of conditions including fatty liver disease, diabetes, insulin resistance and abdominal obesity. The study was published in Nature Medicine.
Traditional BMI is calculated using height and weight. It can be useful for population trends, but it does not measure metabolic function, fat tissue health or early disease processes that may develop before weight changes become obvious.
The new measure, called metabolic BMI or metBMI, is based on metabolomics, which involves measuring hundreds of small molecules in the blood that reflect metabolism. The researchers used those metabolite patterns to estimate whether a person’s metabolic profile resembled patterns more commonly linked with obesity-related dysfunction.
“Our metBMI uncovers a hidden metabolic disorder that is not always visible on the scale,” said Rima Chakaroun, a researcher at Sahlgrenska Academy at the University of Gothenburg and first author of the study. “Two people with the same BMI can have completely different risk profiles depending on how their metabolism and adipose tissue function.”
The study also reported a strong association between metBMI and the gut microbiome. People with higher metBMI tended to have lower microbial diversity and a lower potential to break down dietary fiber into butyric acid, a compound that has been linked in prior research to inflammation and metabolic risk.
“The traditional BMI often misses people who have normal weight but high metabolic risk,” said Fredrik Bäckhed, professor at Sahlgrenska Academy, University of Gothenburg. “metBMI can contribute to a fairer and more accurate assessment of disease risk and thus pave the way for more personalized prevention and treatment.”
The researchers emphasized that metBMI is not a routine clinical tool. Metabolomic testing is not widely available in everyday care, and the study was observational, meaning it cannot prove that the microbiome or specific metabolites cause disease. Still, the findings add to evidence that weight alone can miss meaningful differences in metabolic health.
The study was supported by a combination of public, nonprofit and foundation funding focused on diabetes, cardiovascular health and biomedical research in Sweden and Europe. Major funding sources included the Knut and Alice Wallenberg Foundation, the Swedish Diabetes Foundation, the Swedish Heart and Lung Foundation, the Novo Nordisk Foundation, the Swedish Research Council and Diabetes Wellness Sweden. Additional support came from national research programs in Sweden, the Leducq Foundation and the German Research Foundation.
The research also relied on national supercomputing and imaging infrastructure supported by Swedish research agencies. One author received individual fellowship support and another is funded through a European Research Council award.
Open-access publication was supported by the University of Gothenburg.