The Korean Society for the Study of Obesity (KSSO) has expressed concern over the announcement that the diagnostic criteria for obesity should be raised from the current body mass index (BMI) of 25 kg/m2 to 27 kg/m2 or higher.
Last Friday, the Health Insurance Research Institute under the National Health Insurance Service (NHIS) released a study that the current Korean obesity criteria should be raised to the body mass index (BMI) of 27 or higher when considering the risk of cardiovascular disease and death in Korean adults.
In a statement issued on Wednesday, however, the KSSO struck back, saying, “The research institute's proposal to change the obesity diagnosis criteria was announced without consulting with the KSSO and other related organizations, which leads to confusion about the obesity diagnosis criteria and exerts a negative influence on public health.”
The research institute analyzed the relationship between BMI and all-cause mortality. The result showed that the risk of death was lowest at a BMI of 25 kg/m2, the risk of which steadily increased above it, and the institute cited the finding as a basis for calling for an increase in the obesity diagnostic criteria.
In response, the KSSO said, “We believe that a BMI of 25 kg/m2 or higher, associated with an increased risk of obesity-related chronic diseases, is a valid criterion for obesity. Consideration of obesity comorbidities rather than mortality is intended to prevent complications from obesity because the incidence of obesity comorbidities increases relatively steadily with increasing BMI, whereas mortality varies by population characteristics, such as age, health status, smoking, cause of death, and length of follow-up.”
According to the KSSO’s 2024 Obesity Fact Sheet, a 10-year follow-up of 2012 National Health Checkup participants showed a U-shaped association between BMI and the risk of all-cause mortality, cancer mortality, and circulatory mortality, with a lower risk of death in pre-obese (overweight) and stage 1 obesity (BMI 25-29.9 kg/m²) compared to average weight.
However, the risk of developing chronic diseases, including type 2 diabetes, hypertension, dyslipidemia, and cardiovascular disease, increased with increasing BMI, and the risk increased from the pre-obesity stage compared to normal weight. The incidence of thyroid, colorectal, breast, liver, pancreatic, gallbladder, other biliary tract, and kidney cancer also increased with obesity.
Notably, the risk of developing type 2 diabetes increased by 1.55 times in the pre-obesity stage and 2.46 times in stage 1 obesity compared to normal weight.
“The prevalence of obesity is increasing rapidly in the younger age group of 20 to 50 years,” the obesity society said. “The risk of developing type 2 diabetes, hypertension, dyslipidemia, and cardiovascular disease significantly increased in this age group from the pre-obesity stage compared to older adults. Deaths from these conditions also rose from the pre-obese stage.”
The society emphasized that the purpose of obesity diagnosis is to “prevent and manage the development of complications from obesity” and that diagnostic criteria for obesity should reflect these concerns.
“Recently, the European Association for the Study of Obesity (EASO) changed its guidelines to include a waist-to-height ratio greater than 0.5 or the presence of comorbidities, even at a BMI of 25 kg/m2 or higher. It did so to lower the BMI threshold from 27 kg/m2 to ensure that patients who need treatment receive it on time,” the KSSO said. “Given these trends, the proposal to raise the threshold for obesity diagnosis runs counter to the goal of improving public health by preventing obesity-related comorbidities and complications.”
“If BMI thresholds are set solely based on their association with mortality, many people may underestimate their risk for obesity-related conditions,” it said. “We believe that the diagnostic threshold for obesity should remain at the current BMI of 25 kg/m2 or higher to screen for the risk of obesity-related comorbidities and complications.”