Korean study finds 'obese' BMI may actually be healthiest

In South Korea, a body mass index over 25 is considered "obese," but recent research suggests the healthiest range may actually be higher than that. Health experts are now urging that the threshold be raised to 27.

Oh Sang-woo, a family medicine professor at Dongguk University Ilsan Hospital, recommended raising Korea's obesity threshold to a BMI of 27, noting that the current classification may not currently be ideal.

"Research conducted 20 years ago found that the lowest risk of death was associated with a BMI of 23. But due to changes in people's body types, lifestyle habits and health patterns that have become more similar to those in Western countries, the optimal BMI for the lowest risk of death has shifted to 25," Oh explained.

According to the current standards, a man 173 centimeters tall who weighs 75 kilograms is considered "obese," with a BMI just over 25. However, under the proposed change, the same man would no longer be considered as such, and would still be classified as within a healthy weight range even if he weighs up to 80 kg, according to the NHIS.

Oh was referring to a study by the National Health Insurance Service research institute, which found that a BMI of 25 had the lowest mortality rate within a U-shaped pattern, where mortality and health risks were highest at both the low and high ends of the BMI scale.

The body mass index is a screening tool that measures the ratio of one's height to one's weight to estimate the amount of body fat, expressed in kilograms of weight per meters of height squared. Currently, Korea follows the WHO Western Pacific Region's BMI standards that label a BMI of 18.5-22.9 as "normal," 23-24.9 as "pre-obesity stage," or "overweight," and 25 or above as "obese."

However, the danger of death for those who had a BMI below 18.5 and above 35 was 1.72 times and 1.64 times higher, respectively, than for individuals with a BMI of 25, according to the research.

Lee Sun-mi, the director of the Health Management Research Center at the NHIS research institute, concurred with the need to raise Korea's obesity threshold from the current 25 to 27, noting that China defines a BMI of 28 as the threshold for obesity.

"The NHIS will continue to actively promote health care projects focusing on the country's obese population, who are at a higher risk of developing chronic illness and dying," Lee said in a press release.

The study tracked the risks of all-cause mortality and cardiovascular disease for some 8.47 million adults who underwent health checkups from 2002 and 2003 until 2023.