The risk of premature death associated with obesity has decreased over the past 40 years, according to a new study.
Researchers studied more than 100,000 individuals from Denmark and found that all-cause mortality was higher in obese individuals than in normal weight individuals in 1976-78, but not in 2003-13.
"The increased risk of all-cause mortality associated with obesity compared to normal weight decreased from 30 per cent in 1976-78 to 0 per cent in 2003-13," said Shoaib Afzal from Copenhagen University Hospital in Denmark.
The study also found changes in the Body Mass Index (BMI) associated with the lowest all-cause mortality in three cohorts from Copenhagen, examined respectively in 1976-78, 1991-1994, and in 2003-2013 (all individuals were followed until 2014).
"The optimal BMI for the lowest mortality increased from 23.7 in 1976-78, through 24.6 in 1991-94, to 27 in 2003-13, while individuals with a BMI below or above the optimal value had higher mortality," said Afzal.
"Compared to the 1970's, today's overweight individuals have lower mortality than so-called normal weight individuals," said Borge G Nordestgaard from University of Copenhagen.
"The reason for this change is 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," said Nordestgaard.
"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. That said, maybe overweight people need not be quite as worried about their weight as before," he added.
Obesity and overweight are classified using BMI, calculated as weight in kilogrammes divided by height in metres squared.
A BMI of 25-29.9 represents overweight, a BMI of 30 or greater represents obesity, while a BMI of 18.5-24.9 is considered normal weight. These categories are often used for recommendations on optimum weight, researchers said.
The findings were published in JAMA.
