According to a four-decades-long study of over 100,000 adults in Denmark.
There’s a growing body of evidence that suggests we might want to reevaluate the way we measure an individual’s health — a lower weight doesn’t necessarily equate to better overall health.
According to a new study of over 100,000 adults in Denmark, researchers from the Copenhagen University Hospital have found that those with an “overweight” body mass index (BMI) were more likely to live longer than those in all of the other BMI categories — “normal,” “underweight,” and “obese.”
Through nearly four decades of analysis, from 1976 to 2013, the BMI associated with the lowest risk of death actually shifted from the “normal” weight category to the “overweight” category.
For reference, a BMI between 18.5 and 24.9 is considered “normal” or “healthy,” and a BMI between 25 and 29.9 is considered “overweight.” A BMI of 30 or above is classified as “obese.”
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The results, which appear in the Journal of the American Medical Association, reveal that the BMI associated with the lowest risk of death jumped from 23.7 to 27 during the decades-long study.
"BMI as a number alone may not be sufficient to predict health and risk of death," Rexford Ahima, a physician from the University of Pennsylvania School of Medicine, who wasn’t involved in the study, told Science News. "It has to be taken within context."
Led by clinical biochemist Børge Nordestgaard, the team also found that individuals in the “obese” BMI category ended up with the same risk of death as those in the “normal” BMI range, even after accounting for factors like age, sex, smoking, socioeconomic status, and family history of disease.
This isn’t the first time that a study has raised serious questions about using the BMI scale to measure people’s health. Earlier this year, researchers at the University of California, Santa Barbara found that BMI mislabels 54 million “overweight” and “obese” individuals as unhealthy, while their blood pressure, blood sugar, cholesterol, and insulin levels told a different story.
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"Many people see obesity as a death sentence," lead study author A. Janet Tomiyama, an assistant professor of psychology at the University of California, Los Angeles, said in a press statement. "But the data show there are tens of millions of people who are overweight and obese and are perfectly healthy."
However, these findings aren’t to be used as a “Get Out of Jail Free” card when it comes to staying active and eating healthy.
"Importantly, our results should not be interpreted as suggesting that now people can eat as much as they like, or that so-called normal weight individuals should eat more to become overweight,” said Nordestgaard, the new study’s senior author, in a media release. “That said, maybe overweight people need not be quite as worried about their weight as before.”
Compared to the 1970s, the study shows that the lowest risk of death shifted from “normal” weight individuals to “overweight” individuals, but Nordestgaard says the reason for this change is still unknown.
“However, these results would indicate a need to revise the categories presently used to define overweight, which are based on data from before the 1990's," he says.
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