A recent study published in PLOS One is calling into question what many people have long believed to be true about body mass index (BMI).
After analyzing information from nearly 555,000 adults, the researchers found that having a higher BMI isn’t necessarily going to increase the risk of death.
According to the Centers for Disease Control and Prevention, “Body mass index is a person’s weight in kilograms divided by the square height in meters.” Based on that number, there are four categories: underweight (under 18.5), healthy weight (18.5 - 24.9), overweight (25.0 - 29.9), and obese (30.0 and above).
An easier way to calculate your BMI is by using the National Institutes of Health (NIH) BMI calculator.
Based on the findings from this most recent study, study participants in the overweight group had a similar risk of death as those in the underweight group.
“Our findings suggest that BMI in the overweight range is generally not associated with increased risk of all-cause mortality,” the researchers wrote. “Our study suggests that BMI may not necessarily increase mortality independently of other risk factors in those with BMI of 25.0 - 29.9 and in older adults with BMI of 25.0 - 34.9.”
BMI and mortality risk
For the study, the researchers analyzed data from nearly 555,000 adults, with a mean age of 46, who were enrolled in the National Health Interview Study (NHIS) between 1999 and 2018.
The NHIS was linked with the National Death Index, which allowed the researchers to monitor any participant deaths over the course of the study. The participants self-reported their height and weight, and the researchers calculated their BMIs.
Ultimately, BMI proved to not be a major risk factor when it came to death of any cause among the participants. The risk of death was just about the same for those whose BMI was between 25.0 and 27.4, and for those who fell between 27.5 and 29.9.
The researchers did learn that age came into play a bit. For younger adults with BMI between 22.5 and 27.4, there was no significant increase in the risk of death. However, for adults over 65, that window of BMI without an increase in death was between 22.5 and 34.9.
Overall, participants whose BMI was 30 or above were anywhere between 21% and 108% more likely to die from any cause. Participants in this group were also more than twice as likely to have diabetes or high blood pressure.
Looking to the future, the research team hopes that more factors are taken into consideration when considering consumers’ all-around health status.
“Further studies incorporating weight history, body composition, and morbidity outcomes are needed to fully characterize BMI-mortality associations,” the researchers wrote.