In the present issue, Yu et al.³⁾ evaluated the association between BMI and mortality according to sex in a community-dwelling elderly population. The authors obtained the data from “Living Profiles of Older People Surveys,” which comprised 10,613 community-dwelling South Korean men and women aged 65 years or older. The authors found that the highest survival rates were observed in men with a BMI of 25.0–29.9 kg/m²; a similar trend was observed in women, but this was not statistically significant. These results are similar to findings from previous research, which reported that in cohorts of East Asians, including Chinese, Japanese, and Koreans, the lowest risk of death was seen among persons with a BMI of 22.6 to 27.5 kg/m².⁴⁾

The cut-offs used for the definition of obesity are based on excess morbidity and mortality associated with increasing BMI.¹⁾ There is a significantly increased risk of type 2 diabetes mellitus and hypertension among those with a BMI of 23 to 24.9, as compared to those within the normal range.⁴⁾ In a prospective cohort study of Koreans, the death rate from any cause had a J-shaped association with the BMI.⁵⁾

Therefore, the definition of obesity in Koreans may be different, depending on whether the definition is based on mortality rate or morbidity rate, and it may be the cause of controversy. The WHO Regional Office for the Western Pacific Region also pointed out that the recommendations were provisional and must be revised in the light of further validation studies and clinical experience.¹⁾

This study should cause rethinking of the definition of obesity in Korea, and there should be a serious discussion based on these results.