Compared to the 1970s, the optimal weight for the lowest risk of death has increased dramatically
Carrying some extra weight may not be as dangerous to your health as it was in the 1970s when it comes to the risk of dying, a new Danish study has revealed. The Body Mass Index (BMI), which charts the optimum ratio of height to weight for men and women, has now increased, meaning that those on the upper side of the scale represent the healthy range, according to a report from the Journal of the American Medical Association.
“Compared to the 1970s, today’s overweight individuals have lower mortality than so-called normal-weight individuals,” said Børge Nordestgaard, clinical professor at the University of Copenhagen. ”The reason for this change is unknown.”
The researchers investigated more than 100,000 Danes, dividing them into three subgroups that examined their risk of dying for any reason in the years 1976 to 1978, 1991 to 1994, and 2003 to 2013. In the 1970s, the optimal BMI – calculated by dividing weight in kilos by height in square metres – for the lowest mortality risk was 23.7, the equivalent of a 183cm-tall man weighing 77kg or a 165cm-tall woman weighing 65kg.
By the 1990s, the optimal BMI had risen to 24.6, and for those in the 2003 to 2013 bracket, it had increased again to 27. Anything over 25 in currently considered overweight, while 30 or higher measures as obesity.
In real terms, this means that in 40 years, the optimal low-mortality weight for a man standing 183-cm tall has increased by 14 kilos and by nine kilos for a woman of 165cm.
The Danish researchers also found that men and women with BMI indicating levels of obesity in the 1970s showed a higher risk of death than their slimmer peers, but that this risk had balanced out by the 2000s.
"The increased risk of all-cause mortality associated with obesity compared to normal weight decreased from 30% in 1976 to 78 to zero percent in 2003 to 13," said principal investigator Shoaib Afzal, of Copenhagen University Hospital in Denmark.
While the researchers conceded their findings suggest “a need to revise the categories presently used to define overweight, which are based on data from before the 1990s,” they also pointed out that there are stills risks associated with being overweight, like diabetes and cardiovascular disease. The results should encourage people to be less mindful of what they’re consuming.
"In recent years, as populations become more obese and with wider availability of cheap preventative medications many more such individuals are likely to be better treated for abnormal blood pressure, abnormal cholesterol and, if also present, type 2 diabetes, leading in turn to lower death risks," said Naveed Sattar, professor of metabolic medicine at the University of Glasgow, who commented on the team’s findings.
"In other words, the current findings do not mean that being overweight is protecting you from death, far from it -- rather, many confounding factors may give the current result and we know from many other studies that being overweight or obese does increase mortality risks, in the same way that it increases risk for many other conditions."