In a new study, researchers instead measured what they call metabolic BMI.
It turns out that approximately one tenth of people who are of normal weight according to the conventional BMI scale are at increased risk of conditions such as diabetes and fatty liver.
Two people with the same BMI can therefore have completely different risk profiles, says Rima Chakaroun, a researcher at the University of Leipzig, who was a visiting researcher at the Sahlgrenska Academy in Gothenburg when the study was conducted.
This may involve a two- to fivefold higher risk of fatty liver, diabetes, fat accumulation around internal organs, insulin disorders and inflammation in the group that has an unexpectedly high metabolic BMI.
Not standardized
However, this is not something that can be easily tested, as metabolite measurements are not yet standardized.
We have no value for what is high risk, says Rima Chakaroun.
Unlike standard BMI measurement, which is based on an individual's height and weight, metabolic BMI requires extensive lab testing. The study initially examined 267 different metabolites in the blood of the 1,400 participants.
Metabolites are substances formed during metabolism.
We wanted to find the metabolic signature of increasing BMI and see if we could find that signature even in people who are not overweight.
Fat around the waist
Rima Chakaroun advises against relying solely on the traditional BMI value. Waist circumference tells more about a person's metabolic BMI.
We know for sure that people with a high metabolic BMI have a little more fat around their waist, around their internal organs, and potentially in their liver.
They also have insulin resistance and high insulin levels.
An important finding in the study was the link between high metabolic BMI and poorer bacterial diversity in the gut.
Many of these metabolites are influenced by bacteria. So we have to understand that we don't just live for ourselves, we also live for our bacteria. If we try to make them happy, hopefully we will become metabolically healthy ourselves, says Rima Chakaroun.
The study has been published in Nature Medicine.
