Predicting a person’s risk of death from their body mass index or BMI, which takes both their weight and height into consideration, may be less accurate than previously thought, according to a new report.
The study findings suggest that men, at least, who are classified as overweight according to their body mass index (weight in kilograms divided by weight in meters squared), may actually have a lower risk of death than those classified as normal weight.
“The BMI is the most widely used indicator of relative weight status — too high, too low, just right,” according to study author Jerome Timothy Gronniger, an analyst at the Congressional Budget Office in Washington, DC, told.
However, “It is not especially good at predicting mortality for a large fraction of the population, the broad group of people who are not very obese and not underweight,” he told Reuters Health. Gronniger conducted the researcher while a graduate student at the University of Michigan.
For years, healthcare professionals and researchers have considered a BMI of 20 to 25 to be ideal, and representative of the range for normal-weight individuals. People with a BMI of 25 to 30 are considered overweight, and those with a BMI of 30 or higher are classified as obese.
This definition of obesity was the result of a consensus among the World Health Organization, the Centers for Disease Control and Prevention and various other health bodies. They determined that disease risks increase as an individual’s BMI rises above 25 and that those risks become serious at a BMI of around 30. Still, research has not yet shown a direct link between BMI and mortality risk.