NEW BRUNSWICK, N.J. — While it’s common knowledge that being obese or overweight isn’t ideal for one’s health, surprising new research actually reports that having a higher body mass index (BMI) won’t send an individual to the grave sooner.
The surprising findings from Aayush Visaria and Soko Setoguchi of Rutgers University suggests body mass index (BMI) may not increase mortality independently of other risk factors in adults. BMI’s link with mortality may also vary by age. These findings come from a massive dataset covering over 500,000 American adults spanning two decades.
Obesity has become much more common over the past 25 years, and studies have shown that an elevated BMI may contribute to numerous cardiometabolic conditions. Still, earlier studies that analyzed the association between BMI and all-cause mortality have largely produced inconsistent results. More specifically, the majority of U.S. studies have relied on data collected between the 1960s and 1990s that featured predominantly non-Hispanic White adults.
For this latest project, study authors retrospectively studied data pertaining to 554,332 U.S. adults provided by the 1999-2018 National Health Interview Survey and the 2019 US National Death Index. BMI, meanwhile, was calculated using self-reported height and weight measurements, while participants were divided into nine BMI categories for the analysis.
Information covering the group’s demographics, socio-behavioral factors, co-morbidities, and healthcare access was also made available to researchers. The average person was 46 years-old, with 50 percent being female and 69 percent being non-Hispanic White. Additionally, 35 percent had a BMI between 25 and 30, typically defined as overweight. Another 27.2 percent had a BMI of 30 or higher, falling into the obese category.
Over the course of an average follow-up period of nine years (maximum follow-up period of 20 years), researchers observed a total of 75,807 deaths. All-cause mortality risk was similar across a wide range of BMI categories. Among older adults specifically, the team did not see a significant increase in mortality for any BMI between 22.5 and 34.9, which enters into the BMI categories typically considered obese. Young adults, on the other hand, showed no significant increase in mortality for any BMI between 22.5 and 27.4.
Generally, adults with a BMI over 30 had a 21-percent to 108-percent increased mortality risk that was attributable to their weight. In the general population, these patterns largely remained consistent among both men and women, and across races and ethnicities.
In conclusion, the research team recommends further studies that account for weight history, body composition, and morbidity outcomes to help fully characterize BMI-mortality associations. Still, they believe BMI in the overweight range generally has no association with an increased risk of all-cause mortality.
“Our study highlights the increasing reservations of using BMI alone to drive clinical decisions. There is no clear increase in all-cause mortality across a range of traditionally normal and overweight BMI ranges; however, that is not to say that morbidity is similar across these BMI ranges. Future studies will need to assess incidence of cardio-metabolic morbidities,” the study authors conclude in a media release.
The study is published in PLoS ONE.
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